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	❌	0/7 passing
SOAK	❌	55/56 passing

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 44 lines in your changes missing coverage. Please review.

Project coverage is 78.67%. Comparing base (c2f0349) to head (fb054ab).

Files	Patch %	Lines
agent/csec_metadata.c	0.00%	44 Missing ⚠️

Additional details and impacted files

@@                    Coverage Diff                     @@
##           security-agent-support     #922      +/-   ##
==========================================================
+ Coverage                   78.52%   78.67%   +0.15%     
==========================================================
  Files                         194      194              
  Lines                       27339    27285      -54     
==========================================================
- Hits                        21467    21466       -1     
+ Misses                       5872     5819      -53     

Flag	Coverage Δ
agent-for-php-7.0	77.43% <0.00%> (-0.01%)	⬇️
agent-for-php-7.1	77.15% <0.00%> (-0.04%)	⬇️
agent-for-php-7.2	78.07% <0.00%> (-0.04%)	⬇️
agent-for-php-7.3	78.09% <0.00%> (-0.04%)	⬇️
agent-for-php-7.4	77.80% <0.00%> (-0.04%)	⬇️
agent-for-php-8.0	77.86% <0.00%> (+<0.01%)	⬆️
agent-for-php-8.1	77.85% <0.00%> (+<0.01%)	⬆️
agent-for-php-8.2	77.45% <0.00%> (+<0.01%)	⬆️
agent-for-php-8.3	77.45% <0.00%> (+<0.01%)	⬆️

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