Wait for timeout for ExtPolicy disallowed delete test case

[mgunnala]

Description

Issue #

We are seeing intermittent test failures for the ExtPolicy (ext_policy.py) scenario for the following scenario:

• block custom script with policy, then try to delete -> fails as expected
• allow custom script with policy and retry the delete -> times out when it should succeed

2025-02-03T13:49:24Z.243 [ERROR] ******** [Failed] ExtPolicy: Fail: Unexpected error while trying to delete Microsoft.Azure.Extensions.CustomScript. Extension is allowed by policy so this operation should have completed successfully.
Error: [Delete Microsoft.Azure.Extensions.CustomScript] did not complete within 600 seconds!

This PR makes the following changes to address this issue:

• for the delete on disallowed extension, wait for the full CRP timeout period, remove current workarounds, and move to the last test case
• install guest config during test setup, so it is not automatically installed during the CRP timeout wait period

This PR also makes the following improvements to the test:

• during test setup, only delete extensions being tested, instead of all extensions on the VM
• add try/finally to cleanup policy in the case of test failure

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• New Unit tests were added for the changes made

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[narrieta]

"inadvertently resetting the timeout period" - what are the consequences of that?

btw, GuestConfig is only one of the extensions installed by policy

[mgunnala]

It just makes the test longer - the 15 minute timeout period restarts when CRP gets the GuestConfig enable request. So worst case scenario, GuestConfig is enabled ~14 minutes after the delete request, for a total waiting period of 29 minutes.

What other extensions are installed by policy?

[maddieford]

lgtm

[narrieta]

approved by mistake