feat(grpc): custom incoming server headers

[aldy505]

Description

There are clients such as gRPC KMP client that strictly follow the '-bin' prefix for sending binary values for gRPC metadata. Right now, we can't have a trace propagation due to limitation on header key customization.

Issues

Closes #1328

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Reminders

• Add GH Issue ID & Linear ID
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[aldy505]

Hmm why did go.work.sum changed..

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.67%. Comparing base (1ce3436) to head (ef483df).
⚠️ Report is 156 commits behind head on master.

❗ There is a different number of reports uploaded between BASE (1ce3436) and HEAD (ef483df). Click for more details.

HEAD has 8 uploads less than BASE

Flag	BASE (1ce3436)	HEAD (ef483df)
	9	1

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1360      +/-   ##
==========================================
- Coverage   86.04%   78.67%   -7.37%     
==========================================
  Files          62       90      +28     
  Lines        6090     8268    +2178     
==========================================
+ Hits         5240     6505    +1265     
- Misses        635     1457     +822     
- Partials      215      306      +91     

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