MCP Streamable HTTP Spans (DO NOT MERGE YET)

[umaannamalai]

This PR adds tool manager spans to MCP instrumentation to support streaming.

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Warnings	Elapsed time
✅ ACTION	actionlint	6		0	0	0.82s
✅ MARKDOWN	markdownlint	7	0	0	0	1.18s
✅ MARKDOWN	markdown-link-check	7		0	0	20.84s
✅ PYTHON	ruff	933	0	0	0	0.93s
✅ PYTHON	ruff-format	933	0	0	0	0.35s
✅ YAML	prettier	13	0	0	0	1.36s
✅ YAML	v8r	13		0	0	5.81s
✅ YAML	yamllint	13		0	0	0.63s

See detailed report in MegaLinter reports

[codecov-commenter]

Codecov Report

❌ Patch coverage is 46.66667% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.29%. Comparing base (d1bcc83) to head (b70f97b).

Files with missing lines	Patch %	Lines
newrelic/hooks/adapter_mcp.py	42.85%	3 Missing and 5 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1462      +/-   ##
==========================================
- Coverage   81.33%   81.29%   -0.04%     
==========================================
  Files         209      209              
  Lines       23650    23665      +15     
  Branches     3724     3729       +5     
==========================================
+ Hits        19236    19239       +3     
- Misses       3153     3158       +5     
- Partials     1261     1268       +7     

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