[DOP-7957] Rename mode -> if_exists, and make modes more descriptive

[dolfinus]

Change Summary

• Renamed everywhere mode -> if_exists. New name should be more descriptive than old one, even if it is different from Spark naming.
• For DB connections renamed overwrite and overwrite_table to replace_entire_table. For MongoDB it is replace_entire_collection.
• For Hive renamed overwrite_partitions -> replace_overlapping_partitions (to match FileWriter.Options.if_exists)
• For FileDownloader, FileUploader and FileMover renamed mode values:
• • overwrite -> replace_file (should be more descriptive)
• • delete_all -> replace_entire_directory (for consistent naming with other classes, also more desciptive)
• Old names are automatically converted to new ones for backward compatibility, but with warnings emitted. Added related unit tests.
• Updated integration tests. For Hive added more test cases using parametrize, e.g. writing to partitioned table without passing partitionBy, or vice versa.
• Updated examples and documentation. For Hive updated WriteOptions attributes documentation to match FileWriter.Options (for Spark they its just the same options).

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

Merging #108 (63eedf0) into develop (c97e907) will increase coverage by 0.15%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #108      +/-   ##
===========================================
+ Coverage    93.72%   93.87%   +0.15%     
===========================================
  Files          169      169              
  Lines         7285     7352      +67     
  Branches      1404     1428      +24     
===========================================
+ Hits          6828     6902      +74     
+ Misses         332      328       -4     
+ Partials       125      122       -3     

Files Changed	Coverage Δ
onetl/db/db_writer/db_writer.py	85.41% <ø> (ø)
onetl/connection/db_connection/greenplum.py	75.19% <100.00%> (+0.91%)	⬆️
onetl/connection/db_connection/hive.py	93.58% <100.00%> (+1.14%)	⬆️
onetl/connection/db_connection/jdbc_connection.py	96.05% <100.00%> (+3.38%)	⬆️
onetl/connection/db_connection/jdbc_mixin.py	95.58% <100.00%> (-0.03%)	⬇️
onetl/connection/db_connection/mongodb.py	95.34% <100.00%> (+0.18%)	⬆️
onetl/file/file_downloader/file_downloader.py	95.01% <100.00%> (+0.08%)	⬆️
onetl/file/file_mover/file_mover.py	97.28% <100.00%> (+0.09%)	⬆️
onetl/file/file_uploader/file_uploader.py	94.95% <100.00%> (+0.14%)	⬆️
onetl/file/file_writer/options.py	93.44% <100.00%> (-3.28%)	⬇️
... and 2 more

... and 2 files with indirect coverage changes