fix: stream object copies larger than cloud's CopyObject limit

[vivek-bharathan]

copy now HEADs the source, and when it exceeds 5 GiB, falls back to a streaming multipart copy

[claude]

Claude Code Review

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[codecov]

Codecov Report

❌ Patch coverage is 57.89474% with 32 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
rust/lance-io/src/object_store.rs	57.89%	26 Missing and 6 partials ⚠️

📢 Thoughts on this report? Let us know!

[wjones127]

This looks reasonable to me.

[cmccabe]

@vivek-bharathan : it looks like we need to remove this:

#[cfg_attr(coverage, coverage(off))]

because it's causing some Linux compiler errors:

    error[E0658]: the `#[coverage]` attribute is an experimental feature
    --> rust/lance-io/src/object_store.rs:1568:5
     |
1568 |     #[cfg_attr(coverage, coverage(off))]
     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     |