In most integration tests we already use the pattern of defining the
editor selector once and reusing it in the rest of the test, but it's
not fully consistent everywhere yet. This commit fixes that for the
stamp editor integration tests, which has multiple advantages:
- it improves consistency between the various editor integration tests;
- it removes duplicate function calls and aligns variable definitions;
- it reduces the number of `getEditorSelector` calls and other helper
function calls that contained hardcoded IDs (by updating them to take
editor selectors as arguments instead of editor IDs), which helps to
isolate the tests and to simplify follow-up patches.
0f95617b4c