Draft: fix(issue-6546): trigger token rotation when expiration_days changes

Created an acceptance test TestAccGitlabProjectAccessToken_rotationConfigurationUpdate which confirmed that reducing expiration_days in rotation_configuration did not trigger a token rotation.

Modified the ModifyPlan function in internal/provider/resource_gitlab_project_access_token.go to explicitly check for changes in rotation_configuration.expiration_days.

If a change is detected, it now forces a plan update to rotate the token.

Applied the same fix to internal/provider/resource_gitlab_group_access_token.go after confirming it suffered from the same issue using a new test TestAccGitlabGroupAccessToken_rotationConfigurationUpdate.

closes #6546