add logging assertion in agent

[akalia25]

This PR adds V2 telemetry validation on the Agent E2E test. For each Agent test, there is a list of expectedEvents that the loggedEvents check against, to ensure they fired.

In case of a test failure, it signals either the need to update the expectedEvents list to reflect intentional changes or identifies a potential regression.

The same logging assertion is present in vscode/test/e2e/... and has been very helpful in preventing telemetry regressions.

Test plan

Test via CI and locally with pnpm run test on cody/agent/src/local-e2e

Example of test failing due to missing Event: