Improve performance of HtmlWriter and some smaller things #3138

Job	Run time
JS unit tests	1m 1s
Build all projects without errors	12m 26s
Build published projects without warnings (Release)	5m 17s
Build published projects without warnings (Debug)	2m 48s
.NET unit tests (ubuntu-latest)	3m 1s
UI tests (chrome, ubuntu-latest, Production, Default)	12m 57s
.NET unit tests (windows-2022)	10m 25s
UI tests (chrome, windows-2022, Development, Default)	22m 59s
.NET unit tests (macOS-latest)	6m 33s
UI tests (firefox, ubuntu-latest, Development, Default)	17m 59s
UI tests (firefox, ubuntu-latest, Production, Default)	17m 11s
UI tests (firefox, ubuntu-latest, Development, ExperimentalFeaturesTests)	17m 52s
UI tests (chrome, ubuntu-latest, Production, ExperimentalFeaturesTests)	12m 59s
	2h 23m 28s

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