Fix dynamic form collection reset and parameter uniqueness validation

[LMatt08]

Summary

This PR fixes two issues affecting dynamic form collections:

• Restore the initial collection structure when a form is reset, including rows removed or added after the initial page load.
• Properly unregister the TomSelect form-reset listener when an instance is destroyed.
• Ignore parameters no longer present in their owning Part collection during uniqueness validation. This allows removing a parameter and recreating it with the same name in a single form submission, while still rejecting two simultaneously active parameters with the same name.

These generic changes were extracted from #1492 following review feedback. This PR contains no parameter-definition, choice-list, filtering, migration, or permission changes.

Implementation

The changes are split into two commits:

1. Fix resetting dynamic form collections

   • Restores the initial collection structure on form reset.
   • Cleans up the registered reset listener when TomSelect is destroyed.

2. Ignore removed parameters during uniqueness validation

   • Adds a dedicated repository method used by the UniqueEntity constraint.
   • Considers only parameters still present in the owning Part collection.
   • Adds focused regression tests independent of the parameter-definition feature.

Verification

A negative-control run against the unmodified upstream/master reproduced the issue:

Tests: 2, Assertions: 3, Failures: 1
testRemovedParameterCanBeRecreatedWithTheSameNameBeforeFlush
ERROR: This value is already used.

With the changes applied:

Focused regression tests: 2 tests, 9 assertions — OK
PartParameterTest + PartControllerTest: 46 tests, 72 assertions — OK
PHPStan targeted analysis: OK
ESLint targeted analysis: OK
Yarn production build: OK
git diff --check: OK

The repository currently has no DOM/browser test infrastructure for the JavaScript reset behavior, so the modified JavaScript was verified through ESLint and the production asset build.

[jbtronics]

Thanks for the PR.

I cherry picked the form reset commit.
For the parameter uniquness validation, i implemented a far more generic approach, which implements a custom #[UniqueEntityIgnoringOrphans(fields: ['name', 'group', 'element'], ownerField: 'element')] validator, which just uses doctrine metadata to check that automatically, without the need of a custom repo function.
This can be easily applied to both parameters and attachments for all element types.