Fix test that was not running due to wrong method name

Problem/Motivation

WebformSubmissionResultTest::normalizedElementIdTest() is named with a Test suffix instead of a test prefix, and carries no @test / #[Test] annotation. PHPUnit only collects methods whose name starts with test (or are annotated), so this method is never run.

It is meant to be the only coverage for element-ID normalization across addValidationError(), getOrCreateValidationError() and hasValidationError() (it carries the matching @covers tags). In practice it contributes nothing.

Reviving it also exposes a behavior bug: with the method renamed so it runs, it fails at the existence check that uses the original (un-normalized) element ID, because getOrCreateValidationError() does not store the error it creates. So the test has been hiding a real defect, not just sitting idle.

Steps to reproduce

Rename the method to a test-prefixed name and run the unit test:

ddev phpunit web/modules/custom/graphql_webform/tests/src/Unit/WebformSubmissionResultTest.php

It fails with:

The element ID was normalized when checking for a validation error.
Failed asserting that false is true.
tests/src/Unit/WebformSubmissionResultTest.php (hasValidationError assertion)

Proposed resolution

Rename normalizedElementIdTest() to testNormalizedElementId() so PHPUnit runs it, then make the test pass by resolving the underlying behavior.

The failure is that getOrCreateValidationError() returns a fresh error object without storing it in $this->validationErrors (only addValidationError() stores), so hasValidationError() reports false after a get-or-create. Pick one:

• Option A (keep model behavior): register the error through addValidationError() before asserting existence, and drop the assumption that get-or-create persists.
• Option B (match the "or create" naming): have getOrCreateValidationError() store the created error. Note this changes isValid(), which returns false whenever $this->validationErrors is non-empty; a stored empty error would then mark the submission invalid, so isValid() would need to ignore errors that have no messages.

Remaining tasks

• Rename the method to testNormalizedElementId().
• Choose Option A or B and implement it in src/Model/WebformSubmissionResult.php and/or the test.
• Confirm phpunit, phpcs and phpstan pass.