Adds SGX build using custom 1ES GitHub SGX pool

[ivarprudnikov]

• ADO build pipeline triggers sometimes misfire and leave us in a state where SGX builds do not run, one PR slipped through already
• Main branch builds in ADO pipelines require manual intervention to make sure the build runs
• Created a separate dedicated SGX pool in Azure and scoped it to this repository
• GitHub Action now uses a matrix where one build is virtual as was already and the other uses the custom pool
• Similar to how CCF run their builds (sgx was removed recently): https://github.com/microsoft/CCF/blob/main/.github/workflows/ci.yml