Add more encryption properties to PostHog

[uhoreg]

Fixes https://github.com/element-hq/element-web/issues/27168

Checklist

• [ ] Tests written for new code (and old code if feasible).
• [ ] New or updated public/exported symbols have accurate TSDoc documentation.
• [ ] Linter and other CI checks pass.
• [ ] Sign-off given on the changes (see CONTRIBUTING.md).

[uhoreg]

Sorry, forgot to create this PR as a draft

[uhoreg]

This PR conflicts with https://github.com/matrix-org/matrix-react-sdk/pull/12389 AFAICT, most of it should merge cleanly. Conflicts that I can see off-hand are:

• 12389 removes an argument from the eventDecrypted method, while this PR adds an argument
• both PRs add an argument to the createFailedDecryptionEvent in the test file enable setting properties. This PR needs to set the sender, 12389 needs to set the error code. I've changed createFailedDecryptionEvent in this PR to accept an object with properties to set, rather than trying to decide whether the sender or error code should be the first argument to the function.
• this PR adds test that use the MockDecryptionError class removed in 12389. The tests will need to be adjusted accordingly.

I'd recommend that 12389 gets merged before this one, and I'll handle the conflicts.

[uhoreg]

@BillCarsonFr what does the userTrustsOwnIdentity flag in the PostHog schema represent? I'm trying to figure out how to map it to the functions that the crypto API gives us. Is isCrossSigningReady good enough?

[BillCarsonFr]

@BillCarsonFr what does the userTrustsOwnIdentity flag in the PostHog schema represent? I'm trying to figure out how to map it to the functions that the crypto API gives us. Is isCrossSigningReady good enough?

I think getUserVerificationStatus() would be better

[uhoreg]

merged latest develop

[uhoreg]

Oh, it still needs an Element Web reviewer. I've requested review from Robin and Rich because those were the people GitHub had randomly chosen initially.

[uhoreg]

I think that I've addressed all the requested changes.