Raise TypeError instead of a str in to_bytes and to_str

[CasperGN]

Description

to_bytes and to_str in dapr/clients/grpc/_helpers.py ended with raise f'invalid data type {type(data)}'. Raising a string is itself an error in Python, so a caller who passed the wrong type got TypeError: exceptions must derive from BaseException and never saw the real message. Both now raise TypeError(f'invalid data type {type(data)}'). Callers already got a TypeError, so anyone catching it is unaffected; they just get the right message now. Added unit tests for both helpers. A repo-wide search found no other raise of a string.

RELEASE NOTE: FIX to_bytes and to_str now raise a TypeError with a clear message when given a value that is neither str nor bytes.

Issue reference

Please reference the issue this PR will close: N/A, found while reviewing #1228, no existing issue filed.

Checklist

• Code compiles correctly
• Created/updated tests
• Extended the documentation

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.91%. Comparing base (fb229bc) to head (3544a83).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1229      +/-   ##
==========================================
+ Coverage   83.89%   83.91%   +0.01%     
==========================================
  Files         123      123              
  Lines       10265    10265              
==========================================
+ Hits         8612     8614       +2     
+ Misses       1653     1651       -2     

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[sicoyle]

thank you!

[CasperGN]

Closing in favor of #1220 that came first