feat(hummock): remove combine group for compaction

[Little-Wallace]

Signed-off-by: Little-Wallace bupt2013211450@gmail.com

What's changed and what's your intention?

• remove CombinedGrouping. I have talked with @zwang28. We will split all get/write/flush operations for different group. Of course, the sst files of different group will be also splitted.
• add unit id for sstableinfo for unit aware compaction. See more details in feat(compaction): support sub-level in L0  #3111

Checklist

• I have added necessary unit tests and integration tests
• All checks passed in ./risedev check (or alias, ./risedev c)

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #3138 (3459beb) into main (86c7df1) will decrease coverage by 0.01%.
The diff coverage is 95.00%.

@@            Coverage Diff             @@
##             main    #3138      +/-   ##
==========================================
- Coverage   73.64%   73.63%   -0.02%     
==========================================
  Files         736      736              
  Lines      101586   101514      -72     
==========================================
- Hits        74814    74745      -69     
+ Misses      26772    26769       -3     

Flag	Coverage Δ
rust	73.63% <95.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/storage/src/hummock/sstable/multi_builder.rs	91.09% <80.00%> (+0.04%)	⬆️
...a/src/hummock/compaction/tier_compaction_picker.rs	96.64% <100.00%> (+<0.01%)	⬆️
src/meta/src/hummock/test_utils.rs	95.62% <100.00%> (+0.02%)	⬆️
src/storage/src/hummock/compactor.rs	73.74% <100.00%> (+0.12%)	⬆️
...rc/hummock/shared_buffer/shared_buffer_uploader.rs	87.50% <100.00%> (+0.09%)	⬆️
src/storage/src/hummock/sstable/builder.rs	91.62% <100.00%> (+0.09%)	⬆️
src/storage/src/hummock/sstable/group_builder.rs	95.59% <100.00%> (-0.23%)	⬇️
src/storage/src/hummock/sstable/mod.rs	96.85% <100.00%> (+0.01%)	⬆️
src/storage/src/hummock/test_utils.rs	86.13% <100.00%> (+0.20%)	⬆️

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