[pdata] Fix CopyTo to deep-copy bytes oneof values

[nuromirg]

Description

pcommon.Value.CopyTo performs a shallow copy for ValueTypeBytes. The destination and source Value share the same backing []byte array, so a later mutation of one corrupts the other. This breaks the documented deep-copy contract and propagates to every container that copies an AnyValue (Map.CopyTo, Slice.CopyTo, and any Resource/Scope/attribute copy carrying a bytes value).

CopyAnyValue copies the bytes oneof field by assigning the slice header:

ov.BytesValue = t.BytesValue

so it copies ptr/len/cap fields as well, and the backing array is becoming a shared one.

Ref:

opentelemetry-collector/pdata/internal/generated_proto_anyvalue.go

Line 320 in 1a861f0

ov.BytesValue = t.BytesValue

This PR fixes the copyOther pdatagen template to deep-copy bytes oneof fields, matching the existing copyByteSlice helper, and regenerates the affected code.

Link to tracking issue

Fixes #15621

Testing

Added TestValue_CopyToBytesIsDeepCopy, which copies a bytes Value, mutates the copy, and asserts the source is unchanged (the same approach I used in the issue). The test fails on the previous code and passes with this fix.

Authorship

• I, a human, wrote this pull request description myself.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: nuromirg / name: Nikita R. (ffb5fcb)
• ✅ login: nuromirg / name: Nikita Rudakov (9f249de, b558188)

[dmitryax]

Thanks @nuromirg

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.04%. Comparing base (1a861f0) to head (ffb5fcb).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15622   +/-   ##
=======================================
  Coverage   91.04%   91.04%           
=======================================
  Files         728      728           
  Lines       48455    48455           
=======================================
  Hits        44117    44117           
  Misses       3011     3011           
  Partials     1327     1327           

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