feat: add standalone prop for fields

[logaretm]

What

Sometimes it is useful to have non-controlled inputs, that is inputs that are not tracked by the form.

These inputs typically do not contribute to the form values, nor they have any validation in place other than simple type checks.

A couple of examples on these inputs:

• User choosing an option between A and B with either a radio or select input, which will show some conditional fields based on the selection.
• Fields that will get processed separately without the other inputs in the form

How

This PR adds a standalone configuration property on both Field and useField, this prop allows the field to not be picked up by the form context.

It blocks the inject API in the useField function

[codecov-commenter]

Codecov Report

Merging #3379 (b52ac06) into main (d930271) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #3379   +/-   ##
=======================================
  Coverage   96.70%   96.70%           
=======================================
  Files          65       65           
  Lines        1607     1607           
  Branches      387      389    +2     
=======================================
  Hits         1554     1554           
  Misses         52       52           
  Partials        1        1           

Impacted Files	Coverage Δ
packages/vee-validate/src/Field.ts	94.59% <ø> (ø)
packages/vee-validate/src/useField.ts	98.86% <100.00%> (ø)

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