feat(agent): add server.address field for datastores

[ZNeumann]

This field is needed for some entity relationship mappings (currently only AWS Redshift). Per the spec, this field contains the same data as peer.hostname.

[newrelic-php-agent-bot]

Test Suite	Status	Result
Multiverse	❌	0/8 passing
SOAK	❌	76/79 passing

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.12%. Comparing base (5c0086e) to head (54c4ab1).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1044      +/-   ##
==========================================
- Coverage   77.22%   77.12%   -0.10%     
==========================================
  Files         198      198              
  Lines       27899    27885      -14     
==========================================
- Hits        21544    21506      -38     
- Misses       6355     6379      +24     

Flag	Coverage Δ
agent-for-php-7.2	77.44% <100.00%> (+<0.01%)	⬆️
agent-for-php-7.3	77.46% <100.00%> (+<0.01%)	⬆️
agent-for-php-7.4	77.18% <100.00%> (+<0.01%)	⬆️
agent-for-php-8.0	?
agent-for-php-8.1	?
agent-for-php-8.2	76.58% <100.00%> (+<0.01%)	⬆️
agent-for-php-8.3	76.58% <100.00%> (+<0.01%)	⬆️
agent-for-php-8.4	76.60% <100.00%> (+<0.01%)	⬆️

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[ZNeumann]

Won't do. Backend will instead search for our existing field to establish relationship mapping