Add test cases to test rohmu's handling zero size file

[0xlianhu]

Add test cases to test Rohmu handle zero size files:

Generate an empty file -> compress(lzma/zstd/snappy) and encrypt -> upload (local file system) -> download, decrypt+decompress -> Verify if download files are expected files

Moved this test case to Rohmu instead.

https://github.com/Aiven-Open/rohmu/pull/156

[codecov-commenter]

Codecov Report

Merging #603 (b7a4c9a) into main (6fee738) will decrease coverage by 0.03%. The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #603      +/-   ##
==========================================
- Coverage   91.30%   91.28%   -0.03%     
==========================================
  Files          32       32              
  Lines        4727     4727              
==========================================
- Hits         4316     4315       -1     
- Misses        411      412       +1     

see 2 files with indirect coverage changes

[0xlianhu]

Please see the comments in thread. Also, there are places that also apply but I didn't want to repeat the same comment in several places :).

Thank you very much for your valuable comments. The file was updated according to your comments.

[packi]

The new test doesn't seem to include anything besides rohmu, so it's probably better suited to be in that code base?

[0xlianhu]

Moving the PR to Rohmu repo instead as @packi suggested. https://github.com/Aiven-Open/rohmu/pull/156