feat!: allow passing down existing dataset for write

[wjones127]

BREAKING CHANGE: return value in Rust of write_fragments() has changed to Result<Transaction>.

• Closes Allow passing existing dataset into write_fragments and Dataset::commit() #3058
• Consolidates different implementations of writing and committing into two builders: InsertBuilder and CommitBuilder.
• Allow passing number of commit retries into CommitBuilder.
• Adds Python LanceDataset.insert() method to modify existing datasets.
  • Will be used to fix Table.add resets index_cache_size lancedb#1655
• Closes feat: expose CommitConfig as parameters  #1891

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.79365% with 122 lines in your changes missing coverage. Please review.

Project coverage is 77.14%. Comparing base (4ab270b) to head (7dfb807).

Files with missing lines	Patch %	Lines
rust/lance/src/dataset/write/insert.rs	77.22%	48 Missing and 11 partials ⚠️
rust/lance/src/dataset/write/commit.rs	75.96%	43 Missing and 7 partials ⚠️
rust/lance/src/dataset.rs	76.66%	4 Missing and 3 partials ⚠️
rust/lance/src/dataset/write.rs	14.28%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3119      +/-   ##
==========================================
+ Coverage   77.12%   77.14%   +0.02%     
==========================================
  Files         240      242       +2     
  Lines       80652    80924     +272     
  Branches    80652    80924     +272     
==========================================
+ Hits        62203    62429     +226     
- Misses      15279    15325      +46     
  Partials     3170     3170              

Flag	Coverage Δ
unittests	77.14% <75.79%> (+0.02%)	⬆️

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