Improve dirty state handling

[labkey-nicka]

Rationale

This improves our dirty state handling to catch a couple of cases we are missing:

1. Changes to a SelectInput in a Formsy form are not being recorded as a dirty state change.
2. Nested components that make use of useRouteLeave override beforeunload handling allowing the user to navigate away from dirty page (e.g., from a modal) and not receive an alert.

Related Pull Requests

• Improve dirty state handling #2044
• https://github.com/LabKey/labkey-ui-premium/pull/1002
• https://github.com/LabKey/limsModules/pull/2371

Changes

In useRouteLeave:

• Each consumer now owns its dirty bit; setIsDirty and unmount only affect that bit
• usePrompt and beforeunload now block on the aggregate, so React Router's single-blocker limit no longer masks consumers
• New consumers inherit the dirty state at mount, and one ref-counted beforeunload listener replaces one per consumer

In Formsy:

• isChanged() now uses each input's mount-time pristineValue, not the live value prop a controlled parent overwrites
• resetModel() applies explicit values via resetValue(), making them the new baseline so a reset isn't reported dirty
• withFormsy skips re-applying a value the input already holds, dropping a redundant validation and duplicate onChange