Backend: fix build (remove XamEssentials code) #2487

Job	Run time
macOS--mono	1m 46s
windows--dotnet6	7m 35s
windows--legacyFramework	20m 36s
macOS--dotnet6-and-mono	9m 23s
linux22-github--newmono	4m 46s
linux22-github	4m 10s
linux22-vanilla--stockdotnet6	5m 24s
linux22-vanilla--stockmono	6m 4s
linux20-github	5m 55s
linux20-vanilla--newmono	3m 46s
linux20-github--newmono	5m 35s
linux20-vanilla--stockmono	7m 1s
linux22-vanilla--stockdotnet6-and-newmono	7m 22s
linux22-vanilla--newmono	3m 50s
linux22-vanilla--stockdotnet6-and-stockmono	5m 27s
conventions	0s
snap_pkg	0s
	1h 38m 40s

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