AfformScanner - Simplify cache. Fix CLI/web sync bug.

AfformScanner - Simplify cache. Fix CLI/web sync bug.

Example bug:

1. Find a packaged (non-overriden) form - e.g. `mockPage`
2. Run `cv api4 Afform.update +w name=mockPage +v permissions='*always allow*'
3. Run `curl http://localhost/civicrm/mock-page`
4. Observe: the page-load fails even though the permissions say it should work

The call to `Afform.update` should trigger a cache-clear, but it only fixes
on the CLI...  because the CLI and web have different runtime IDs.

The runtime-id was included preventively in anticipation that oddball
multisite arrangements might need to store these things separately.  But I
think it's overdone, because the runtime-ID factors in things like
`SCRIPT_FILENAME` which has no bearing on the whether to use the same cache.

Let's KISS and *if* there's any kind of multisite issue, then we can revisit.