refactor: move lance-namespace into lance repo

[jackye1995]

No description provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.91931% with 362 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.75%. Comparing base (85d44b6) to head (958ae2b).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
rust/lance-namespace-impls/src/rest.rs	56.13%	216 Missing and 2 partials ⚠️
rust/lance-namespace-impls/src/dir.rs	90.88%	49 Missing and 17 partials ⚠️
rust/lance-namespace/src/namespace.rs	0.00%	48 Missing ⚠️
rust/lance-namespace-impls/src/connect.rs	0.00%	20 Missing ⚠️
rust/lance-namespace/src/schema.rs	89.89%	0 Missing and 10 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4978      +/-   ##
==========================================
- Coverage   81.81%   81.75%   -0.06%     
==========================================
  Files         335      340       +5     
  Lines      135486   136884    +1398     
  Branches   135486   136884    +1398     
==========================================
+ Hits       110847   111916    +1069     
- Misses      20952    21247     +295     
- Partials     3687     3721      +34     

Flag	Coverage Δ
unittests	81.75% <73.91%> (-0.06%)	⬇️

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[Xuanwo]

I'm ok with this PR after all CI pass.