Expose a public toggle for disable_transaction_file (skip redundant external transaction file)

Background

Every commit currently writes the transaction in two places:

• Inline in the manifest (transaction_section) — written unconditionally. do_write_manifest sets manifest.transaction_section whenever a transaction is passed (rust/lance-table/src/io/manifest.rs:153-159), and all commit paths pass Some(transaction) (rust/lance/src/io/commit.rs:265,842,1047).
• A separate _transactions/ file — written whenever !disable_transaction_file() (rust/lance/src/io/commit.rs:151,786,981).

FLAG_DISABLE_TRANSACTION_FILE (bit 32, rust/lance-table/src/feature_flags.rs:22) and the commit-path support already exist to skip the now-redundant external file. But disable_transaction_file lives only on the internal pub(crate) struct ManifestWriteConfig (rust/lance/src/dataset.rs:3438) and is never set to true anywhere — no WriteParams/CommitConfig field, no Python/Java binding, no env var, no config key, not even in tests.

So the optimization is plumbed end-to-end except for the one switch that turns it on, and we pay one redundant write per commit.

Ask

Wire up a public way to enable disable_transaction_file:

• Plumb it through a user-facing surface (e.g. WriteParams / CommitConfig, with Python and Java bindings kept as thin wrappers), keeping the parameter name consistent across languages.
• Add tests covering: a commit with the external file disabled produces a readable dataset from the inline transaction_section, and the writer feature flag (bit 32) is set.

Note: enabling it sets a writer feature flag, so older readers that don't understand bit 32 will reject the dataset. Defaulting it on is tracked separately (see follow-up issue).

Start by tracing ManifestWriteConfig in rust/lance/src/dataset.rs into the commit paths in rust/lance/src/io/commit.rs, then inspect the flag definition in rust/lance-table/src/feature_flags.rs and transaction handling in rust/lance-table/src/io/manifest.rs. Identify the user-facing write configuration and its Python and Java wrappers. Done means callers can enable the option, a commit remains readable from the inline transaction_section, and writer feature flag bit 32 is set.