Improve typings of getNativeFormProps

[kestarumper]

This PR closes #1037 by improving .getNativeFormProps by guaranteeing key and onChange props and replacing any with unknown.

[codecov]

Codecov Report

Merging #1044 (749f92a) into master (eafe38e) will decrease coverage by 0.38%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1044      +/-   ##
==========================================
- Coverage   98.98%   98.59%   -0.39%     
==========================================
  Files         202      202              
  Lines        3156     3214      +58     
  Branches      798      829      +31     
==========================================
+ Hits         3124     3169      +45     
- Partials       32       45      +13     

Impacted Files	Coverage Δ
packages/uniforms/src/BaseForm.tsx	100.00% <ø> (ø)
packages/uniforms/src/AutoForm.tsx	100.00% <100.00%> (ø)
packages/uniforms/src/QuickForm.tsx	100.00% <100.00%> (ø)
packages/uniforms/src/ValidatedForm.tsx	100.00% <100.00%> (ø)
packages/uniforms-material/src/TextField.tsx	87.50% <0.00%> (-12.50%)	⬇️
packages/uniforms-material/src/NumField.tsx	89.47% <0.00%> (-10.53%)	⬇️
packages/uniforms-material/src/DateField.tsx	91.30% <0.00%> (-8.70%)	⬇️
packages/uniforms-material/src/SubmitField.tsx	93.33% <0.00%> (-6.67%)	⬇️
packages/uniforms-material/src/NestField.tsx	94.11% <0.00%> (-5.89%)	⬇️
packages/uniforms-material/src/ErrorsField.tsx	94.11% <0.00%> (-5.89%)	⬇️
... and 7 more

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