Update build pipeline to meet EO requirements

[JatinSanghvi]

• Generate SBOM manifests for NuGet and Maven packages.
• Use 1ES hosted pool for builds.
• Remove requirement of build script files.
• Remove requirement to update CSPROJ and POM files between successive releases.
• Have builds triggered by to-be-created v1.x branch for commits pertaining to previous releases.
• Generate artifacts for builds triggered due to tag-commit. These artifacts would be used in releases.
• Refactor build jobs and steps.

Sample builds for review.

1. Tag-commit triggered: https://dev.azure.com/azfunc/Azure%20Functions/_build/results?buildId=45171&view=results
2. Branch-commit triggered: https://dev.azure.com/azfunc/Azure%20Functions/_build/results?buildId=45170&view=results

Note: The code for above builds is same except that they use .NET 6. We would be moving to .NET 6 once v1.x branch is forked out from dev.