RATIONALE

We plan to move from a single alias-domain configuration to a multi company
enabled support for alias domains and aliases. First step to prepare this
change is to cleanup alias usage through various Odoo addons.

ALIAS USAGE CLEANUP

Cleanup alias usage and definition. Prepare code to ease future changes and
improvements. Notably

  * add a 'alias_email' computed field on the mixin allowing to have the
    complete alias email when set, and False in case it is inactive or linked
    to an inactive alias domain;
  * remove unnecessary alias_id field definition when just the help differs
    from the standard definition coming from the 'mail.alias.mixin';
  * use fields coming from 'inherits' instead of using alias_id and its sub-
    fields; notably use 'alias_display_name' and 'alias_email' fields;
  * remove useless custom code and management;
  * improve alias parameters support code in configuration parameters;

ALIAS MIXIN WITH OPTIONAL ALIAS_ID

Some models would like to use the 'mail.alias.mixin' but it creates an alias
for each record in the parent model. This leads to a lot of unused aliases
if only a subset of those records really use aliases i.e. a lot of aliases
with 'alias_name' being 'False'.

In this commit we introduce a new mixin 'mail.alias.mixin.optional' that
behaves like the old 'mail.alias.mixin' but without having the 'alias_id'
field required i.e. without the "inherits". When creating a record without
giving an 'alias_name' no alias is created.

In this PR we use it notably to remove custom code in account journal model
and make it more standard. Using it in more models will be done later, but
it is a candidate to cleanup unused aliases related to discuss channel model.

ALIAS NAME SANITIZE

Currently there is a constraint on alias name as we allow only a subset of
valid latin characters in it aka `[a-zA-Z0-9!#$%&'*+\-/=?^_`{|}~]`. There
is also an automatic sanitize of alias name at create / write that replaces
any non-word characters by an hyphen. This sanitize is stricter than the
constraint and it is not really coherent.

In this commit we make the sanitize inlined with the constraint, allowing
more characters to go through the 'mail.alias.mixin' cleaning pass notably.

Enforce that void alias names are forced to False to avoid any constraint
issue. Sanitize method is now independent from the check method, to avoid
calling multiple times the sanitization as it is often used for other checks.

MISC

Lint / reorder code, prepare future changes. Add tests, notably for alias
name sanitize and management.

Provide various fixes, see sub commits for more details.

LINKS

After odoo/odoo#130768 and odoo/enterprise#45204 this is another preparation
for multi-company aliases (see odoo/odoo#76734 and odoo/enterprise#20983).

Task-3453343 (Mail: Cleanup Alias Usage)
Prepares Task-36879 (Mail: Support MultiCompany Aliases)