[Datasets] Patch Parquet file fragment serialization to prevent metadata fetching.

[clarkzinzow]

Alternative to #22580.

TODOs

• Verify performance improvement on nightly test (need to wait for PR wheel build).

Related issue number

Closes #21274

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[clarkzinzow]

@ericl Got ~18s when running the nightly test, so the results are:

• Status quo: 150s
• Custom partition file implementation: 13s
• (This PR) Custom file fragment serialization: 18s

Given that this PR adds a lot less tech debt, I think that going with this PR over the other makes sense. What do you think?

[ericl]

Agreed, this LGTM as a much cleaner short-term fix.