[Feature Request] Set Build Env variables to skip Federated tests

[gladjohn]

MSAL client type

Confidential

Problem statement

ADFS servers are down and federated tests are failing

Proposed solution

Implement DoNotRunFederatedTestsAttribute in Test.Common/TestUtilities, gate on MSAL_SKIP_FEDERATED_TESTS, convert the [Ignore] blocks from PR #5415, wire the env‑var in CI.

Alternatives

No response