[AppSec] Automated user ID collection modes

[Anilm3]

Description

This PR introduces the new user ID collection modes (ident, anon, disabled) which replace the old ones (safe, extended, disabled). Some interesting facts:

• ident mode is now the default one, meaning the user IDs are always collected.
• Metadata is no longer included on ident or anon mode.
• All relevant headers are now collected on ident or anon mode.
• Some of the functionality has been moved to user_tracking.*, in preparation for further work on authenticated user tracking.

The system tests will fail due to the change on login events, however they have been updated here: https://github.com/DataDog/system-tests/compare/anilm3/php-user-events-v2?expand=1

The remote configuration changes have not been included in this PR given the ongoing work being done on the helper.

Related Jira: APPSEC-53749

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 69.69697% with 30 lines in your changes missing coverage. Please review.

Project coverage is 79.17%. Comparing base (471a64f) to head (8cdfe4f).

Files	Patch %	Lines
appsec/src/extension/tags.c	61.70%	9 Missing and 9 partials ⚠️
appsec/src/extension/user_tracking.c	76.92%	5 Missing and 7 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2782      +/-   ##
============================================
- Coverage     79.27%   79.17%   -0.10%     
  Complexity     2452     2452              
============================================
  Files           169      169              
  Lines         18018    18052      +34     
  Branches        904      913       +9     
============================================
+ Hits          14283    14293      +10     
- Misses         3245     3264      +19     
- Partials        490      495       +5     

Flag	Coverage Δ
appsec-extension	69.27% <69.69%> (-0.37%)	⬇️
tracer-extension	79.21% <ø> (ø)
tracer-php	82.88% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
appsec/src/extension/configuration.c	62.62% <ø> (ø)
appsec/src/extension/configuration.h	100.00% <ø> (ø)
appsec/src/extension/user_tracking.c	71.69% <76.92%> (+6.88%)	⬆️
appsec/src/extension/tags.c	79.86% <61.70%> (-2.71%)	⬇️

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