FEAT: MMAP storage backend

[ChengjieLi28]

What do these changes do?

Use mmap as storage backend. Now Xorbits can run the complete TPCH SF100 queries on a single MacOS laptop with 32GB memory.

Future work:

• Use shm as the main storage, and use the mmap as spill storage.

Check code requirements

• [x] tests added / passed (if needed)
• [x] Ensure all linting tests pass

[codecov[bot]]

Codecov Report

Merging #674 (a949b7a) into main (feacc2e) will decrease coverage by 0.27%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #674      +/-   ##
==========================================
- Coverage   93.59%   93.33%   -0.27%     
==========================================
  Files        1025     1026       +1     
  Lines       79733    79812      +79     
  Branches    16538    16563      +25     
==========================================
- Hits        74625    74490     -135     
- Misses       3430     3665     +235     
+ Partials     1678     1657      -21     

Flag	Coverage Δ
unittests	93.22% <100.00%> (-0.27%)	:arrow_down:

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

Files Changed	Coverage Δ
python/xorbits/_mars/deploy/oscar/local.py	97.05% <100.00%> (+0.07%)	:arrow_up:
python/xorbits/_mars/storage/__init__.py	69.23% <100.00%> (+2.56%)	:arrow_up:
python/xorbits/_mars/storage/mmap.py	100.00% <100.00%> (ø)

... and 25 files with indirect coverage changes