Flaky tests

[BMurri]

Describe the bug
Several tests will fail from time to time due to the forward passage of time (e.g. ArmUrlTransformationStrategyTests.TransformUrlWithStrategyAsync_CallTwiceForSameStorageAccount_CachesKey)

Steps to Reproduce
Steps to reproduce the behavior:
Run tests. Sooner or later, a test will incorrectly fail because some component of time included in the comparison will have changed enough to generate an unexpected result (e.g. creating a sas with a cached user key with an expiration datetime that is one second later than the reference sas).

Expected behavior
A clear and concise description of what you expected to happen.
Tests that don't depend on a portion of the test completing within some arbitrary time interval (e.g. within the same second of wall-clock time).

Additional context
Add any other context about the problem here.

  Failed TransformUrlWithStrategyAsync_CallTwiceForSameStorageAccount_CachesKey [2 ms]
  Error Message:
   Assert.AreEqual failed. Expected:<https://foo.blob.core.windows.net/?skoid=8d61b50e-e71e-4ea7-a53d-0a443ff67bb3&sktid=e6d03617-7c83-4d25-95c9-aa47ac129de1&skt=2024-01-09T05%3A16%3A39Z&ske=2024-01-09T06%3A16%3A39Z&sks=SIGNED_SERVICE&skv=V1_0&sv=2022-11-02&se=2024-01-16T05%3A16%3A39Z&sr=c&sp=r&sig=fXBaEzjzTwJsoPIjT1XJl%2Fn8EjlxDqT%2FdgDwTCY4MV4%3D>. Actual:<https://foo.blob.core.windows.net/?skoid=8d61b50e-e71e-4ea7-a53d-0a443ff67bb3&sktid=e6d03617-7c83-4d25-95c9-aa47ac129de1&skt=2024-01-09T05%3A16%3A39Z&ske=2024-01-09T06%3A16%3A39Z&sks=SIGNED_SERVICE&skv=V1_0&sv=2022-11-02&se=2024-01-16T05%3A16%3A40Z&sr=c&sp=r&sig=1pdOXMwx4BGnE2XHWymVcKjP5kgCffuQTRG1gOP1NVY%3D>. 

Note that the user delegation key is identical in both tokens, but the expiration date/time is one second later. The two tokens were obtained one right after the other.

Fixing this will require mocking the "system clock" or repeating tests/portions of tests as appropriate to report correct test results without clock skews producing false test failures.