CLDSRV-925: UploadPartCopy handle checksums

[leif-scality]

• Handle checksums in UploadPartCopy. Don't compute and store a checksum for parts in external backends (same as PutPart).
• fix: CompleteMPU don't require per-part checksums for external backends. UploadPart and UploadPartCopy don't store a checksum for external backend parts so we cannot require them. The final object will not have a checksum.
• fix: UploadPart reject Parts missing a COMPOSITE checksum when required
• fix: UploadPart returning the default checksum when it should not
• fix: CopyObject allow in-place checksum change on self-copy

UploadPartCopy — when the checksum is recomputed vs reused vs skipped

#	MPU algorithm	Dest backend	copy-source-range present	Source's stored checksum	Checksum action	Returned in CopyPartResult?
1	none (legacy MPU, pre-feature)	any	any	any	None — nothing stored/returned	–
2	client-provided (explicit) or default (implicit crc64nvme)	external (aws_s3 / azure / gcp / …)	any	any	None — skipped, matches UploadPart	no
3	client-provided (explicit) or default (implicit crc64nvme)	local (sproxyd / file / mem)	yes (ranged)	any	Recompute — over the copied range	explicit: yes · default: no (stored only)
4	client-provided (explicit) or default (implicit crc64nvme)	local (sproxyd / file / mem)	no	FULL_OBJECT, same algorithm	Reuse — copy source's stored value	explicit: yes · default: no (stored only)
5	client-provided (explicit) or default (implicit crc64nvme)	local (sproxyd / file / mem)	no	COMPOSITE, different algorithm, or none	Recompute — over the whole part	explicit: yes · default: no (stored only)

[bert-e]

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[bert-e]

Incorrect fix version

The Fix Version/s in issue CLDSRV-925 contains:

• None

Considering where you are trying to merge, I ignored possible hotfix versions and I expected to find:

• 9.4.0

Please check the Fix Version/s of CLDSRV-925, or the target
branch of this pull request.

[codecov]

⚠️ JUnit XML file not found

The CLI was unable to find any JUnit XML files to upload.
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[claude]

LGTM

Review by Claude Code

[claude]

• Test names using it() should start with "should" (tests/unit/api/objectCopyPart.js — multiple tests)
  - Prefix each test name with "should" (e.g. 'should return true when...')
  - Prefer assert.match over assert(err.message.includes(...)) for substring assertions (tests/functional/aws-node-sdk/test/object/mpuUploadPartChecksum.js — lines 136, 247)
  - Use assert.match(err.message, /expected checksum Type/) for clearer failure output
  
  Review by Claude Code