fix(fields): don't enforce mandatory fields on automated item creation

[MyvTsv]

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes !46291 !45954

Root cause

Mandatory custom fields were enforced unconditionally, even for items created without any human filling a form (tickets generated by the Mail Collector) Since there is no way to fill a mandatory custom field from an incoming email, item creation was silently rejected with "Some mandatory fields are empty".

Fix

Mandatory field enforcement in PluginFieldsContainer::validateValues() is now
skipped when any of the following applies:

• the code runs from the command line (isCommandLine())
• the code runs inside a cron task, internal or external (Session::isCron())
• the item is being created through GLPI core's "automated import" marker
  (_auto_import), set by MailCollector::buildTicket() and by recurring
  tickets, this covers the "Collect now" button too, which is a plain web
  request (neither CLI nor cron), so it wasn't covered by the first two checks
  alone.

Steps to reproduce

1. Create a "dom" container for Ticket with a mandatory custom field and no
   default value.
2. Configure a mail collector.
3. Trigger an import (cron task, or the "Collect now" button on the collector).
4. Before the fix: the ticket is rejected ("Some mandatory fields are
   empty"), even though there is no way for the sender to fill that field.
   After the fix: the ticket is created normally.

[Rom1-B]

This only relaxes mandatory checks for CLI/cron/_auto_import (Ticket-only). !46291's actual scenarios (Inventory agent, REST API bulk import) go through plain HTTP requests and never set any of these. Can you also check is_dynamic (set by src/Glpi/Inventory/**) and isAPI() in inc/container.class.php:1743?

[Rom1-B]

Move the unset into the existing tearDown() so it always runs, even if the assertion above fails.

This isn't the only line in this case; please process them all.

[Rom1-B]

The new isAPI() / is_dynamic bypass paths in isMandatoryCheckBypassed() have no test coverage. Can you add a case for an inventory-created item (is_dynamic) and one for an API-created item (isAPI()) skipping mandatory validation?