Add --tags option to s3 cp, mv, and sync commands

[luigi617]

Issue #, if available:
Resolve: #2458

Description of changes:
Add --tags to s3 cp, mv, and sync (inline object tagging on upload)

Adds a repeatable --tags <key> <value> option to the high-level s3 cp, mv, and sync commands so users can set S3 object tags inline as part of an upload, instead of making a separate s3api put-object-tagging call afterward. It reuses the same --tags key value syntax already used by s3 mb.

• Added --tags examples to cp.rst, mv.rst, and sync.rst.

S3-S3 copy is out of scope of this PR.

Testing

• Unit tests + Functional tests
• Verified end-to-end against a real bucket, all tags are added as expected.

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