feat(Payroll): allow overwriting tax component through additional salary

[ruchamahabal]

In some months, users might want to overwrite the auto-calculated tax amount through additional salary. While overwriting component amount works for other types of components, it was not supported for tax components. Added support for the same

This is only applicable if the additional salary has Overwrite Salary Structure Amount enabled

Added validation + warning for both cases:

no-docs This works as expected now like overwriting other components. Doesn't require an explicit mention as such

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 73.68421% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 72.83%. Comparing base (fdf986b) to head (a2739db).
Report is 5 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1600   +/-   ##
========================================
  Coverage    72.83%   72.83%           
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  Files          202      202           
  Lines        11169    11188   +19     
========================================
+ Hits          8135     8149   +14     
- Misses        3034     3039    +5     

Files	Coverage Δ
hrms/payroll/doctype/salary_slip/salary_slip.py	86.30% <80.00%> (-0.06%)	⬇️
...oll/doctype/additional_salary/additional_salary.py	68.14% <66.66%> (-0.13%)	⬇️

... and 1 file with indirect coverage changes