Add Intermediate-Context header support for Talaria message metadata

[ChaitanyaSingla]

This PR introduces the intermediate-context header as an optional field in the metadata preparation flow for both online and offline messages sent by Talaria.

Key Changes:

1. Added support for intermediate-context header in message metadata construction.
2. Updated relevant structs and interfaces to include the new header.

Purpose:
The intermediate-context header allows for carrying any extra information that may be required by the receiving systems.

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.67%. Comparing base (75b7bf1) to head (921af14).
⚠️ Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
device/mocks.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1160      +/-   ##
==========================================
- Coverage   81.79%   81.67%   -0.13%     
==========================================
  Files         150      150              
  Lines        7214     7220       +6     
==========================================
- Hits         5901     5897       -4     
- Misses       1124     1135      +11     
+ Partials      189      188       -1     

Flag	Coverage Δ
unittests	81.67% <90.90%> (-0.13%)	⬇️

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[denopink]

I made 1 change, updated the implementation to match device.newDevicecurrent options pattern for consistency

[denopink]

fyi releasing and then updating xmidt-org/talaria#558, if anything break then I'll patch it