Revise arm64_unix_skip_list in runtest.py

[MichalStrehovsky]

Found by accident when messing with the script in the runtimelab repo. We should probably revise the arm64_unix_skip_list.

This looks like an ARM64 bringup workaround from more than 2 year ago - I couldn't find associates issues. At this point it's probably just causing us to not have crossgen test coverage on ARM64 because I don't see what should be ARM64 specific on Microsoft.CodeAnalysis.VisualBasic.

runtime/src/coreclr/tests/runtest.py

Lines 1188 to 1193 in c48127d

	arm64_unix_skip_list = [
	".*Microsoft.CodeAnalysis.VisualBasic.*",
	".*System.Net.NameResolution.*",
	".*System.Net.Sockets.*",
	".*System.Net.Primitives.*"
	]

[am11]

Same case with other skip lists (skip_list, unix_skip_list) in this file. e.g. System.Runtime.WindowsRuntime.UI.Xaml project was deleted in #36715.

[mangod9]

since crossgen is no longer used this has part of the script has now been removed.