lsp-roslyn: fix arm64 detection and use default window/logMessage handler #5490

Job	Run time
test (ubuntu-latest, 27.2, false)	2m 9s
test (ubuntu-latest, 28.2, false)	2m 33s
test (ubuntu-latest, 29.4, false)	2m 42s
test (macos-latest, 28.2, false)	4m 29s
test (macos-latest, 29.4, false)	3m 53s
test (windows-latest, 27.2, false)	3m 15s
test (windows-latest, 28.2, false)	3m 30s
test (windows-latest, 29.4, false)	3m 44s
test (ubuntu-latest, snapshot, true)	1m 50s
test (macos-latest, snapshot, true)	2m 59s
test (windows-latest, snapshot, true)	6m 46s
	37m 50s

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