pipelines: Major improvements

[bwateratmsft]

Fixes #2173

Example PRs using these:

• Extension: Try out the new pipelines vscode-containers#365
• NPM: Try out the new pipelines vscode-docker-extensibility#334

Successful builds using these:

• Extension: https://devdiv.visualstudio.com/DevDiv/_build/results?buildId=13199244&view=results
• NPM:

Successful releases using these:

• Extension:
• NPM:

[bwateratmsft]

TODO: reenable

Suggested change

	# Invoke-Expression $commandLine # TODO: temporarily disabled for testing
	# if ($LASTEXITCODE -ne 0) {
	# Write-Error "Failed to publish VSIX: $($vsix.vsixName)"
	# exit 1
	# }
	Invoke-Expression $commandLine
	if ($LASTEXITCODE -ne 0) {
	Write-Error "Failed to publish VSIX: $($vsix.vsixName)"
	exit 1
	}

[bwateratmsft]

TODO: Need to create the branch ruleset