refactor(agent): expose app metadata for csec via global symbol

[lavarou]

Rather than providing a PHP user function to expose app metadata to PHP userland, export a global symbol for cseg agent to use.

[newrelic-php-agent-bot]

Test Suite	Status	Result
Multiverse	❌	0/8 passing
SOAK	❌	78/79 passing

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 2.08333% with 47 lines in your changes missing coverage. Please review.

Project coverage is 77.27%. Comparing base (6b66d77) to head (2f616e1).

Files with missing lines	Patch %	Lines
agent/csec_metadata.c	0.00%	44 Missing ⚠️
agent/php_minit.c	25.00%	3 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##           security-agent-support     #922      +/-   ##
==========================================================
- Coverage                   77.74%   77.27%   -0.47%     
==========================================================
  Files                         199      199              
  Lines                       27938    27785     -153     
==========================================================
- Hits                        21721    21472     -249     
- Misses                       6217     6313      +96     

Flag	Coverage Δ
agent-for-php-7.2	77.40% <2.08%> (-0.69%)	⬇️
agent-for-php-7.3	77.42% <2.08%> (-0.69%)	⬇️
agent-for-php-7.4	77.13% <2.08%> (?)
agent-for-php-8.0	76.53% <2.08%> (-0.68%)	⬇️
agent-for-php-8.1	77.03% <2.08%> (-0.57%)	⬇️
agent-for-php-8.2	76.64% <2.08%> (-0.57%)	⬇️
agent-for-php-8.3	76.64% <2.08%> (-0.57%)	⬇️
agent-for-php-8.4	76.66% <2.08%> (-0.57%)	⬇️

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[anmol-ap]

@ZNeumann @lavarou @bduranleau-nr
Could you please review the PRs now.

• The config has been moved to a separate config file at csec agent.
• newrelic.security.agent.enabled and newrelic.security.enabled are read in the APM agent for logging purpose.
• Metadata required by csec agent has been exposed by api.
• We are going ahead with separate installation approach as decided.

Related PRs :
#933
#922
#918

[anmol-ap]

Rebased the branch.