chore: replace paste with pastey

[DCjanus]

• # Which issue does this PR close?

• Closes parquet relies on unmaintained dependency paste #7598

Rationale for this change

cargo deny flags the unmaintained paste crate, so advisory checks fail until we remove it. Switching to the maintained drop-in replacement keeps the dependency tree healthy and restores the advisory gate.

What changes are included in this PR?

• Replace all paste dependencies with pastey across Arrow Flight, Parquet, and Parquet Variant crates.
• Update source files to import pastey::paste instead of paste::paste.
• Refresh Cargo.lock so it pulls in pastey.

Are these changes tested?

• cargo check -p parquet
• cargo deny check advisories

Are there any user-facing changes?

No user-facing changes or API adjustments.

[alamb]

I feel like there might actually be more risk with a new crate than sticking with the old crate -- even if it is 'unmaintained' if it doesn't need maintenance then what is the harm

If we really want to remove the dependency on paste, I think it would be better to vendor it into arrow (aka copy the relevant parts we need)

[alamb]

Thank you for this contribution @DCjanus

[DCjanus]

I feel like there might actually be more risk with a new crate than sticking with the old crate -- even if it is 'unmaintained' if it doesn't need maintenance then what is the harm

I think I'm convinced, perhaps we can keep things as they are for now, until one day we need to change it