Add response token count logic to Bedrock instrumentation.

[umaannamalai]

This PR updates sync and async Bedrock instrumentation and tests to pull token counts directly from the response object. If a customer has an LLM token counting callback function registered, this will still take priority over the response token count values.

It also removes token count calculations from error cases as the agent will consistently stop reporting token counts when a error was met during the creation of a text generation.

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	6		0	0	0.76s
✅ MARKDOWN	markdownlint	7	0	0	0	1.24s
✅ MARKDOWN	markdown-link-check	7		0	0	20.57s
✅ PYTHON	ruff	940	2	0	0	0.94s
✅ PYTHON	ruff-format	940	2	0	0	0.35s
✅ YAML	prettier	13	0	0	0	1.41s
✅ YAML	v8r	13		0	0	6.86s
✅ YAML	yamllint	13		0	0	0.61s

See detailed report in MegaLinter reports

[codecov-commenter]

Codecov Report

❌ Patch coverage is 86.66667% with 14 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.73%. Comparing base (b1408de) to head (777e0d1).

Files with missing lines	Patch %	Lines
newrelic/hooks/external_botocore.py	88.00%	7 Missing and 5 partials ⚠️
newrelic/config.py	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@                     Coverage Diff                      @@
##           feature-llm-token-counts    #1504      +/-   ##
============================================================
- Coverage                     81.48%   80.73%   -0.76%     
============================================================
  Files                           209      210       +1     
  Lines                         23815    23955     +140     
  Branches                       3753     3770      +17     
============================================================
- Hits                          19406    19340      -66     
- Misses                         3153     3350     +197     
- Partials                       1256     1265       +9     

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