Re-enable user actions (angular v16/eslint update broke some xapian things subtly)

[castaway]

Does this fix the user actions issues? Maybe
Does it pass tests? Not on my machine..

After a stern talking to, passes tests and user actions work !

[piratefinn]

The xapian revert makes sense to me. The Sentry PR (50b8e5d) switched declare var to declare let and changed some .apply() calls to use spread syntax, and this just puts it all back to the state that was working. The Observable<boolean> tightening on deleteLocalIndex is a nice bonus over what master had.

ESLint approach is a bit inconsistent (blanket /* eslint-disable */ in the two loader files vs targeted // eslint-disable-next-line no-var in the other three) but totally fine given the loader files already had a stack of rule disables.

E2E changes look good. Adding cy.intercept + cy.wait before assertions is definitely the right move over relying on 10s timeouts. Splitting the subaccount tests out into their own file keeps things tidy. The mockserver receipt endpoint fix is a reasonable defensive change too.

Minor thing: double space in declare var IDBFS; in both loader files, and the PR title says "revert(index)" but it touches the loader/patching code as well. Neither worth changing.