Azure OpenAI: Upgrade TestFramework to STJ 6.0.9

[annelo-msft]

The Azure.AI.OpenAI library is not able to upgrade to Azure.Core 1.43.0 or SCM 1.1.0 because those bring in a transitive dependency on STJ 6.0.9, where some APIs from STJ 4.7.2 have been obsoleted, and so the library will not build.

#45961 pins the Azure.Core version and opts AOAI CI's out of pipeline stages that replace the Azure.Core and SCM package references with project references.

Once SCM 1.1.0 has released, as part of the upgrade for the GA release of OAI and AOAI, we'll need to remove the version overrides and project reference exclusions added in #45961, #44896, and #44825.

Related to #44899

[annelo-msft]

Once this item is complete, we can merge #46011 as well.