Forms: Improve consistancy in html for consent and checkbox fields

### Impacted plugin

Jetpack

### Quick summary

Currently the checkbox field and the "explicit" consent field have different HTML markup, even thought the end result is almost he same.
A checkbox and a label.

Checkbox


Consent Field.


It would be good to have these fields the same (expect for block specific classes) so that they are easier to style.

### Steps to reproduce

1. Add the forms block.
2. Add the checkbox block and the consent block ( select the "explicit" option in the block settings).
3. Notice that the html that was produce is different.

### Site owner impact

Fewer than 20% of the total website/platform users

### Severity

Moderate

### What other impact(s) does this issue have?

No revenue impact

### If a workaround is available, please outline it here.

_No response_

### Platform (Simple and/or Atomic)

Simple, Atomic, Self-hosted

Start by reproducing the forms block with a checkbox and an explicit consent field, then inspect the generated HTML for both fields. Compare their markup and identify where each field is rendered; done means the structures match apart from block-specific classes and remain styleable consistently.

Written by the indexing model from the issue text.