feat: introduces sync gRPC server

[ab93]

• udf multi-threaded sync server
• udsink multi-threaded sync server
• udf and udsink sync servers with migration threadpool

Note: Since most of the changes are in the server function, the codecov is failing.

Closes #25

[codecov[bot]]

Codecov Report

Merging #27 (d5b0e70) into main (b6a4bc0) will increase coverage by 10.84%. The diff coverage is 92.30%.

@@             Coverage Diff             @@
##             main      #27       +/-   ##
===========================================
+ Coverage   87.45%   98.29%   +10.84%     
===========================================
  Files           6        6               
  Lines         271      235       -36     
  Branches       13       14        +1     
===========================================
- Hits          237      231        -6     
+ Misses         32        2       -30     
  Partials        2        2               

Impacted Files	Coverage Δ
pynumaflow/function/server.py	95.74% <87.50%> (+25.05%)	:arrow_up:
pynumaflow/sink/server.py	95.12% <87.50%> (+27.81%)	:arrow_up:
pynumaflow/function/_dtypes.py	100.00% <100.00%> (ø)
pynumaflow/sink/_dtypes.py	100.00% <100.00%> (ø)

:mega: We’re building smart automated test selection to slash your CI/CD build times. Learn more

[vigith]

I wonder whether we should do an integer multiple of CPUs available as the default value? The number of CPUs as thread pool size is too low.