feat: Able to change dynamically field name

[deandreamatias]

Connection with issue(s)

Close #1173

Solution description

If update name field of same widget, works fine

Screenshots or Videos

Screencast.from.22-01-23.01.54.38.webm

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 #1178 (2468d2b) into main (4a3db67) will decrease coverage by 0.36%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1178      +/-   ##
==========================================
- Coverage   84.35%   83.99%   -0.36%     
==========================================
  Files          19       19              
  Lines         703      706       +3     
==========================================
  Hits          593      593              
- Misses        110      113       +3     

Impacted Files	Coverage Δ
lib/src/form_builder_field.dart	79.01% <0.00%> (-3.04%)	⬇️

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