Make indexer::prepared_commit public

[dcecile]

The PreparedCommit struct is returned by IndexWriter::prepare_commit() for use by developers, so it should be public.

The docstring for prepare_commit() links to the docs for PreparedCommit, but the link doesn't work because the module is private.

It is an error to try to use the module directly because its parent is private:

17  | use tantivy::indexer::PreparedCommit;
    |              ^^^^^^^ private module
    |
note: the module `indexer` is defined here

Note: currently with the module private, it is still possible to use the struct:

let mut prepared_commit = index_writer.prepare_commit()?;
prepared_commit.set_payload("TEST");
prepared_commit.commit()?;

[codecov-commenter]

Codecov Report

Merging #1184 (e51deff) into main (e2fbbc0) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1184      +/-   ##
==========================================
- Coverage   93.99%   93.98%   -0.02%     
==========================================
  Files         204      204              
  Lines       34558    34558              
==========================================
- Hits        32482    32478       -4     
- Misses       2076     2080       +4     

Impacted Files	Coverage Δ
src/indexer/mod.rs	100.00% <ø> (ø)
src/lib.rs	98.85% <ø> (ø)
src/directory/file_watcher.rs	96.69% <0.00%> (-3.31%)	⬇️
src/indexer/segment_serializer.rs	98.07% <0.00%> (-1.93%)	⬇️
src/postings/stacker/expull.rs	93.44% <0.00%> (-0.44%)	⬇️
src/postings/postings_writer.rs	98.04% <0.00%> (+0.48%)	⬆️
src/directory/watch_event_router.rs	96.18% <0.00%> (+0.76%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e2fbbc0...e51deff. Read the comment docs.