feat: pass vended credentials to Iceberg native scan

[tokoko]

Closes #3522.

What changes are included in this PR?

• obtains object storage credentials from FileIO objects through reflection and merges them with hadoop properties that are passed to native scanner.
• there is SupportsStorageCredentials interface in latest iceberg which should eventually make reflection code less ugly, but we can't use it yet.
• updates RestCatalogAdapter test utility to enable fake credential vending for testing.
• this won't handle credential refresh in case temporary credentials expire. that's much harder problem to tackle.

How are these changes tested?

• tested with RestCatalogAdapter that injects minio credentials into LoadTable response objects.
• a negative test with wrong temporary credentials to make sure that it's the vended credentials that are being used rather than the ones set in hadoop configuration.

[mbutrovich]

Thank you for the PR @tokoko! I'm thrilled that others are trying to improve the native Iceberg integration. I will take a look today.

[mbutrovich]

Thanks again @tokoko. This looks really close! I have a few small suggestions.

[mbutrovich]

Thanks for the great improvement, @tokoko! Approved pending CI.