A running task/ticket timer can sometimes stutter, show negative values, and track the wrong elapsed time.

### Steps to reproduce

On a record with a timesheet timer (for example, a Field Service task):

1. Start the timer and let it run for about 15-20 seconds.
2. Stop it and confirm the dialog.
3. Start it again. This creates a new `timer_start`.
4. Reload the page.

The timer starts jumping every second between two different values. As it keeps running, it can even show negative values such as `00:00:-57`.

If the problem does not appear right away, repeat steps 2-4 a few times. It usually shows up after a few stop/start/reload cycles.

### Cause

The timer shown in the button bar is the `timer_start_field` widget. It starts a `setInterval` that updates a shared `TimerReactive` object once per second.

While a form is loading, Odoo renders it several times in a row (for example: a first render, another when the chatter is loaded, and another when the record data comes back from the server). Rendering a form builds all of its fields to produce the display, so each of these renders creates its own `timer_start_field`. Odoo keeps and mounts only the render that ends up on screen; the earlier ones are thrown away before being mounted.

The interval is started while the field renders, from the record observer set up in `setup`, before the field is mounted. So the fields that are later thrown away also start an interval. Those intervals keep running for the rest of the session. Each one updates the same shared `TimerReactive` object using the `timer_start` it was created with.

As long as every instance has the same `timer_start`, they all write the same value and the problem stays hidden. After the timer is stopped and started again, the old instances keep the old `timer_start` while the mounted one uses the new one. Every second they overwrite each other's value, so the timer jumps between two different elapsed times. When the instance with the newer `timer_start` writes right after one with an older start, it tries to show a smaller elapsed time than what is already there, and the subtraction in `TimerReactive` produces a negative number of seconds.

### Fix

Move the per-second timer update into a `useEffect`. The effect only runs after the field is mounted, and Owl automatically cleans it up when the field is unmounted or when `timer_start` or `timer_pause` change.

This means fields that are destroyed before they are mounted never start an interval, so only the mounted field updates the shared timer.

`onRecordChange` no longer starts or stops the interval. It only updates the displayed timer value to match the current record.

opw-6209405

Forward-Port-Of: odoo/enterprise#126242

Steps to reproduce:

- Create a product with a bom and 2 operations
- Create an MO for 1 unit of that product
- Confirm the MO
- On the bom, delete the second operation and modify the first operation on anything else than the company, name or workcenter
- Go back to the MO, click the "Update Bom" button
> The second operation is not unlinked and the first operation is not
  updated

Cause of the issue:

The `action_update_bom` updates the move raws and operations of the MO via the `_link_bom`:
https://github.com/odoo/odoo/blob/f66614193cce18f5a3298d03ce7e5f29d54f07e9/addons/mrp/models/mrp_production.py#L1214-L1218 For draft MO's all the work of these updates is done via the compute methods and by deleting all the records unrelevant to the new bom: https://github.com/odoo/odoo/blob/f66614193cce18f5a3298d03ce7e5f29d54f07e9/addons/mrp/models/mrp_production.py#L2603-L2626 And, in that case all the workorders that are not linked to an operation of the bom are expected to be deleted. However, when the MO is not in draft, the update of operations is expected to be performed here: https://github.com/odoo/odoo/blob/f66614193cce18f5a3298d03ce7e5f29d54f07e9/addons/mrp/models/mrp_production.py#L2647-L2664 However, since the operation of the bom has been deleted, the workorder that is expected to be deleted is not linked to any operation and hence does not satisfy the condition to be deleted:
https://github.com/odoo/odoo/blob/f66614193cce18f5a3298d03ce7e5f29d54f07e9/addons/mrp/models/mrp_production.py#L2663-L2664 Concerning the non update of operations, it happens because the MO's operation are only updated on the three fields: `company_id`, `workcenter_id`, `name`:
https://github.com/odoo/odoo/blob/31df5033e31c193b4576ef37dfbc5fc683817bc5/addons/mrp/models/mrp_production.py#L2647-L2664 https://github.com/odoo/odoo/blob/31df5033e31c193b4576ef37dfbc5fc683817bc5/addons/mrp/models/mrp_production.py#L2628-L2629 However, many other cahnges can and are actually relevant.

Note:

Prior to commit 80e6ed658fb43584bc2fad673ca40d9af6cf0ab6 operations were archived on boms rather than deleted:
https://github.com/odoo/odoo/blob/4a5270218fe6fd7d30edb6d684b3340dc7423bab/addons/mrp/views/mrp_routing_views.xml#L53-L55 As such they would still be linked to an operation (but unrelated to the present values of the bom) and hence would fall into the condition of being unlinked from the MO.

Since the bom operations are no longer archived there is no way to determine if an operation used to be linked to a bom and we therefore need to chose between deleting all operations unrelated to the present bom or to keep them all (when the MO has been confirmed).

Community: https://github.com/odoo/odoo/pull/269747

opw-6285878
opw-6261738

Forward-Port-Of: odoo/enterprise#122746
Forward-Port-Of: odoo/enterprise#120709