feat: added unsetValueOnUnmount config

[logaretm]

🔎 Overview

This PR adds a configuration to change the automatic behavior of unsetting field values when the components are unmounted.

The configuration is available on both the form level and the field level.

useField('name', undefined, { keepValueOnUnmount: true });

useForm({ keepValuesOnUnmount: true });

<Field name="fieldName" keep-value />

<Form keep-values>
....
</Form>

✔ Issues affected

closes #3795
closes #3607

[codecov-commenter]

Codecov Report

Merging #3815 (8efdf95) into main (3d582ec) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3815      +/-   ##
==========================================
+ Coverage   96.46%   96.48%   +0.01%     
==========================================
  Files          68       68              
  Lines        1895     1904       +9     
  Branches      473      479       +6     
==========================================
+ Hits         1828     1837       +9     
  Misses         67       67              

Impacted Files	Coverage Δ
packages/vee-validate/src/Field.ts	97.46% <ø> (ø)
packages/vee-validate/src/Form.ts	100.00% <ø> (ø)
packages/vee-validate/src/useField.ts	98.80% <100.00%> (+<0.01%)	⬆️
packages/vee-validate/src/useForm.ts	98.29% <100.00%> (+0.03%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3d582ec...8efdf95. Read the comment docs.