feat(forms): Implement new strategies for SLM config fields

[ccailly]

Checklist before requesting a review

Please delete options that are not relevant.

• 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

This pull request introduces three new SLM (Service Level Management) field strategies for the advancedforms plugin, allowing more flexible configuration of SLA/OLA dates based on form answers or submission date. It also updates the configuration system to support these new strategies.

New SLM Strategies:

• Added three new SLM field strategies for advanced date handling in SLA/OLA fields:
  • SpecificDateAnswerSLMStrategy: Sets the SLA/OLA date based on a specific date question's answer in the form.
  • ComputedDateFromFormSubmitDateSLMStrategy: Computes the SLA/OLA date using the form submission date plus/minus a configurable offset (minutes/hours/days/months).
  • ComputedFromSpecificDateAnswerSLMStrategy: Computes the SLA/OLA date using a specific date answer from the form plus/minus a configurable offset.

The integration of this PR required the integration of certain core modifications in order to support the addition of policies from a plugin.

Screenshot

Available strategies for TTO / TTR / Internal TTO / Internal TTR