FIO-9159: add intentionallyHidden ephemeral state and breaking change to clearOnHide behavior

[brendanbond]

Link to Jira Ticket

https://formio.atlassian.net/browse/FIO-9159

Description

The platform has always treated an intentionally hidden component (i.e. one with the hidden property checked) as the same as conditionally hidden. This, combined with the fact that the clearOnHide property defaults to true, means that the the server would likely clear any intentionally hidden container's (e.g. Container component, Edit Grid, Nested Form, etc.) data. For a long while, however, there was a bug that meant that Nested Forms would not behave this way.

This PR aims to simplify and codify the behavior of hidden components - the clearOnHide property will now clear data only when that component is conditionally hidden. Intentionally hidden components will be unaffected and their data will not be cleared.

Breaking Changes / Backwards Compatibility

This fundamentally is a breaking change, because it decouples intentionally hidden components from conditionally hidden ones. It needs to be included in a changelog as breaking and released as part of a major version.

Dependencies

n/a

How has this PR been tested?

Added automated tests around clearOnHide

Checklist:

• I have completed the above PR template
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• My changes include tests that prove my fix is effective (or that my feature works as intended)
• New and existing unit/integration tests pass locally with my changes
• Any dependent changes have corresponding PRs that are listed above