Add agent_language to serverless payload.

[umaannamalai]

This PR updates lambda metadata inside the serverless protocol as per the serverless specs.

[github-actions]

🦙 MegaLinter status: ❌ ERROR

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	bandit	1		0	4.83s
✅ PYTHON	black	2	1	0	1.31s
❌ PYTHON	flake8	2		1	0.53s
✅ PYTHON	isort	2	1	0	0.2s
✅ PYTHON	pylint	2		0	3.96s

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.58%. Comparing base (13d726b) to head (a00c605).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1140      +/-   ##
==========================================
- Coverage   81.67%   81.58%   -0.09%     
==========================================
  Files         193      193              
  Lines       21333    21333              
  Branches     3716     3716              
==========================================
- Hits        17423    17404      -19     
- Misses       2826     2843      +17     
- Partials     1084     1086       +2     

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[hmstepanek]

Pre-approving. Just a minor fixup I think.