The goal of this task is to update jQuery from version 1.11 to 3.x.
Task-id : 1896658

As we are skipping 2 major versions, there are some breaking changes in the jquery library described here: https://jquery.com/upgrade-guide/3.0/

Main changes are:
-------------------------
1. Update the libraries jQuery, jQueryUI, QUnit and select2 to their latest version.
   The link to generate the build of jQueryUI with the used components: [jquery UI build](https://jqueryui.com/download/#!version=1.12.1&components=111110010101111110100010110000011010000000000000)
2. Use native promises ([a complete explanation about promises here](https://github.com/getify/You-Dont-Know-JS/blob/master/async%20%26%20performance/ch3.md)) everywhere possible:
In order to [be A+ compliant](https://promisesaplus.com/), the jq3 deferred uses `setTimeout(..., 0)`
for every then and catch, which takes between 4 and 10 ms by call.

    This would be way too slow to use in Odoo.
    To prevent this, we have used the native Promises everywhere possible.
    Be it with jq deferred or native promises, all promises are now asynchronous,
    this example will ALWAYS result in printing first "just after blabla" then "blabla"
    because the `then` function will always be asynchronous (opposite to
    what jquery used to do)
    ```javascript
    function () {
        Promise.resolve("blabla").then(console.log);
        console.log("just after blabla");
    }

    // console:
    // just after blabla
    // blabla
    ```


3. On native promises, you should see the catch like a try/catch in
javascript, meaning that it will catch all errors including coding errors:
    For this we have introduced the concept of `guardedCatch`, which will be executed
    on promise rejection unless the promise is rejected because there is
    a code error or runtime error (calls on undefined, etc).

4. Native Promises do not have `done`, `fail` and `always` methods nor does it have the `state` method

    - `fail` can be replaced with `guardedCatch`
    - `return $.when(x).done(function() ...)` can be replaced with

    ```javascript
    var x = Promise.resolve(x); // we get the x promise in a local variable, without then
    x.then(function() ...); // we add a new handler to x. This operation returns a new promise we don't care about
    return x; // we return the x promise that will be completed without waiting for the then
    ```

    - `$.when().done(function ...)` without the return can be replaced by `then(function ....)`, because if it is not returned, it doesn't matter what is chained or not `$.when().always(function() ...)` can be replaced with
    ```javascript
    var always = function() ...
    Promise.resolve().then(always).guardedCatch(always);
    ```

    - It is not possible to inspect the state of a promise, except in debug tools of chrome and firefox. Any code that relies on `$.Deferred.state()` should be rewritten to use flags in `then` and `catch` handlers. Remember that it is not possible to execute the handlers in a synchronous manner, so when a promise is created, its `then` will never be called on the same execution stack. At best it will be called on the next microtask tick (before the next setTimeout).

5. We have introduced the concept of guardedCatch, to copy the behavior of the old fail:
   The guarded catch will only execute the handler in parameter if the rejection reason is not an `Error`
    ```javascript
    var failingPromise = Promise.reject({message:"I am the rejection reason"});
    failingPromise.guardedCatch(function(reason) {console.log(reason);}); // is called, then returns a rejected promise
    failingPromise.catch(function(reason) {console.log(reason);}); // is called
    ```
    will write the reason "I am the rejection reason" to the console twice: once because the `guardedCatch` will execute (and return a rejected `Promise` with the same reason it was called), a second time because the `catch` will catch the rejected reason returned by the `guardedCatch`
    ```javascript
    var promiseWithError = Promise.resolve().then(function() {
        a.b = 0;  // <-- the variable a does not exist, so a.b is an error
    });
    promiseWithError.guardedCatch(function(reason) {console.log(reason);}); // will not be called
    promiseWithError.catch(function(reason) {console.log(reason);}); // will be called
    ```
    contrary to how deferred used to work, here the catch will be called because it behaves like a `try... catch...` and will catch the coding error like if it was a business error. The `guardedCatch` however does not call the handler if the rejection reason is an error.

    In all Odoo code, we never reject a promise with an error and always use objects to defined the rejected reason, so it is a good idea to use `guardedCatch` everywhere.

6. Native Promises can have only one parameter passed to a `then` function or a `catch` function:
    `xxx.then(function(param1, param2) {...}); // param2 will never have a value`

    - we can replace `$.when(prom1, prom2).then(function(result1, result2) { ... });` by
    ```javascript
    Promise.all([prom1, prom2]).then(function(results) {
        var result1 = results[0];
        var result2 = results[1];
        ...
    });
    ```

7. We are now using ES7 code in the unit tests (async await).

Co-authored-by: Aaron Bohy <aab@odoo.com>
Co-authored-by: Christophe Matthieu <chm@odoo.com>
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>
Co-authored-by: David Monjoie <dmo@odoo.com>
Co-authored-by: Martin Geubelle <mge@odoo.com>
Co-authored-by: svs-odoo <svs@odoo.com>
Co-authored-by: Vincent Schippefilt <vsc@odoo.com>