fix: improve focus fields on validation

[deandreamatias]

Connection with issue(s)

Close #1230

Solution description

• Remove force validation on autovalidation enables modes
• Only focus on invalid field when no focus in another field
• Only focus on invalid field when focusOnInvalid is true

Screenshots or Videos

Screen.Recording.2023-05-18.at.10.18.18.mov

Screen.Recording.2023-05-18.at.10.18.53.mov

To Do

• Read contributing guide
• Check the original issue to confirm it is fully satisfied
• Add solution description to help guide reviewers
• Add unit test to verify new or fixed behaviour
• If apply, add documentation to code properties and package readme

[codecov]

Codecov Report

Merging #1254 (8cfd21a) into main (ab3b8f7) will decrease coverage by 0.29%.
The diff coverage is 85.71%.

@@            Coverage Diff             @@
##             main    #1254      +/-   ##
==========================================
- Coverage   85.14%   84.86%   -0.29%     
==========================================
  Files          20       20              
  Lines         707      707              
==========================================
- Hits          602      600       -2     
- Misses        105      107       +2     

Impacted Files	Coverage Δ
lib/src/form_builder_field.dart	81.91% <80.00%> (ø)
lib/src/form_builder.dart	75.55% <100.00%> (ø)

... and 1 file with indirect coverage changes

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