feat: add initial scanner statistics

[westonpace]

This just captures some very basic statistics. I'd like to eventually add bytes read, decode time, and time waiting on I/O to the mix. However, those will need to wait for #2977 because those stats will go in the scheduler and we want one scan scheduler to be used in the entire plan first.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 56.73077% with 45 lines in your changes missing coverage. Please review.

Project coverage is 77.60%. Comparing base (9e18322) to head (3a25450).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
rust/lance/src/dataset/scanner/stats.rs	45.94%	40 Missing ⚠️
rust/lance/src/dataset/scanner.rs	80.00%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3075      +/-   ##
==========================================
+ Coverage   77.57%   77.60%   +0.03%     
==========================================
  Files         240      241       +1     
  Lines       78683    79129     +446     
  Branches    78683    79129     +446     
==========================================
+ Hits        61040    61411     +371     
- Misses      14498    14573      +75     
  Partials     3145     3145              

Flag	Coverage Δ
unittests	77.60% <56.73%> (+0.03%)	⬆️

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