object: reuse encrypted data across put retries

[Light-City]

1.Why and Backgroud?

cachedStore.upload retries failed object uploads by calling ObjectStorage.Put again. For encrypted storage, each attempt previously reread and re-encrypted the same data block, generating a new data key, nonce, and ciphertext. This introduced unnecessary CPU and memory overhead, especially when timed-out attempts overlapped with subsequent retries.

related issue: #7325

2.How to fix?

This change creates a request-scoped context shared by all attempts of one logical Put. encrypted.Put encrypts the payload once and reuses the prepared ciphertext for subsequent attempts, with synchronization for overlapping retries and isolation between different encryption instances. Regular Put calls without this context keep their existing behavior, and storage wrappers require no additional interfaces as long as they propagate the context.

[codecov]

Codecov Report

❌ Patch coverage is 97.29730% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 55.07%. Comparing base (44a5657) to head (b2214e0).
⚠️ Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/object/encrypt.go	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7396      +/-   ##
==========================================
- Coverage   56.32%   55.07%   -1.25%     
==========================================
  Files         177      139      -38     
  Lines       59011    48866   -10145     
==========================================
- Hits        33236    26913    -6323     
+ Misses      22259    19041    -3218     
+ Partials     3516     2912     -604     

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