fix(dispatcher): catch validation errors in outbound sendEvent/sendCreate

[triemerge]

Rationale

The inbound dispatch() path catches validator errors, but the outbound sendEvent/sendCreate side doesn't seem to. A validation failure there can go uncaught and take down the driver process.

Followed the same isUnderTest() convention used elsewhere in this file.

Fixes #41865

[dcrousso]

this is likely far too broad of a catch-all (i.e. it could mask other legitimate bugs that need fixing)

[triemerge]

Yeah that makes sense, reverted the sendCreate change and also narrowed the remaining sendEvent catch to ValidationError only while at it.

[dcrousso]

i dont think we can safely just drop this as the object has been created (i.e. a future operation with the same guid will fail)

[triemerge]

Agreed, the dispatcher is already registered at that point so just returning would leave things in a weird state. Would you prefer the sendCreate path handled separately or is it fine to leave that for a follow up?

Edit: for the sendCreate path, one option could be catching in the Dispatcher constructor instead, where we have access to undo the registration. That way there's no ghost object. happy to add that here if it makes sense..