Add optional check_finite flag to process_x

[patelshivani2283-lab]

This PR adds an optional check_finite argument to process_x.

By default it is set to True, so the existing behavior stays the same.
If set to False, it skips the NaN/Inf check (assert_all_finite).

This can be useful in cases where the data is already validated and the extra check is not needed.

[patelshivani2283-lab]

This is an initial step toward #1717. I can extend this to propagate the flag through posterior classes if needed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.31%. Comparing base (937efc2) to head (dd290ee).
⚠️ Report is 43 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1828      +/-   ##
==========================================
- Coverage   88.54%   86.31%   -2.23%     
==========================================
  Files         137      143       +6     
  Lines       11515    17753    +6238     
==========================================
+ Hits        10196    15324    +5128     
- Misses       1319     2429    +1110     

Flag	Coverage Δ
fast	82.77% <100.00%> (?)

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Files with missing lines	Coverage Δ
sbi/utils/user_input_checks.py	76.80% <100.00%> (+0.12%)	⬆️

... and 77 files with indirect coverage changes