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 analysis: Success

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	7		0	0	0.89s
✅ MARKDOWN	markdownlint	7	0	0	0	1.31s
✅ PYTHON	ruff	946	0	0	0	1.0s
✅ PYTHON	ruff-format	946	0	0	0	0.35s
✅ YAML	prettier	15	0	0	0	1.46s
✅ YAML	v8r	15		0	0	4.92s
✅ YAML	yamllint	15		0	0	0.62s

See detailed reports in MegaLinter artifacts

[codecov-commenter]

Codecov Report

❌ Patch coverage is 90.90909% with 10 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (feature-llm-token-counts@7d5adac). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
newrelic/hooks/external_botocore.py	90.90%	6 Missing and 4 partials ⚠️

Additional details and impacted files

@@                     Coverage Diff                     @@
##             feature-llm-token-counts    #1504   +/-   ##
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  Coverage                            ?   79.91%           
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  Files                               ?      207           
  Lines                               ?    24037           
  Branches                            ?     3802           
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  Hits                                ?    19208           
  Misses                              ?     3583           
  Partials                            ?     1246           

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[hmstepanek]

I said this in a comment too but I'm going to stop reviewing this for the moment.

Can you for the sake of being able to easily identify what's changed here: re-order these changes in the file such that they end up being diffed against the original function. Right now it's really hard to compare to see what's changed because the diff isn't showing a 1:1 comparison. I know it's a pain but in a larger PR like this with lots of files changed it makes it a ton easier to review.

[hmstepanek]

Just a couple minor suggestions and one question-otherwise looks good.

[hmstepanek]

I don't think the default values of "" are reachable here given the if msg.get("content").