[Task] Fix tests' warnings on missing wrapping act

Starting to see these similar warnings in many places in tests:

```bash
console.error
Warning: An update to Popper inside a test was not wrapped in act(...).

When testing, code that causes React state updates should be wrapped into act(...):

act(() => {
/* fire events that update state */
});
/* assert on the output */

This ensures that you're testing the behavior the user would see in the browser. Learn more at https://reactjs.org/link/wrap-tests-with-act
at Popper (/home/thvo/workspace/cryostat-web/node_modules/@patternfly/react-core/dist/js/helpers/Popper/Popper.js:28:26)
at GenerateId (/home/thvo/workspace/cryostat-web/node_modules/@patternfly/react-core/dist/js/helpers/GenerateId/GenerateId.js:20:5)
at Select (/home/thvo/workspace/cryostat-web/node_modules/@patternfly/react-core/dist/js/components/Select/Select.js:33:5)
at Component (/home/thvo/workspace/cryostat-web/src/app/Settings/CredentialsStorage.tsx:75:43)
at Wrapper (/home/thvo/workspace/cryostat-web/src/test/Common.tsx:59:30)

```

Seem to affect tests on component that has a Popper in its sub-tree. Maybe some deps upgrade update Popper somewhere?

Start by reproducing the warning in tests for components containing PatternFly Popper, using the stack-trace locations in src/app/Settings/CredentialsStorage.tsx and src/test/Common.tsx as entry points. Trace which test interactions trigger the update and verify that the relevant tests complete without missing-act warnings while preserving their existing assertions.

Written by the indexing model from the issue text.