[Feature] Avoid recording the same app launch error multiple times #2919

Description

The same exception can currently be recorded multiple times in app launch telemetry.

In appLauncher.ts, the error handler calls generator.addError() and then rethrows the exception. The rethrown exception is subsequently caught by TelemetryGenerator.time(), which automatically calls addError() again.

As a result, a single app launch failure may produce duplicate telemetry properties such as:

error.code0 = <error code>
error.code1 = <same error code>