Add Marker's "opacity" option and "setOpacity" method #3464

Job	Run time
Code Hygiene	1m 59s
Render tests (ubuntu-latest, 0)	7m 33s
Unit tests and Coverage	1m 51s
Render tests (ubuntu-latest, 1)	5m 53s
Render tests (ubuntu-latest, 2)	5m 18s
Build tests (ubuntu-latest)	2m 57s
Integration tests (ubuntu-latest)	3m 55s
Render tests (windows-latest, 0)	8m 14s
Build tests (windows-latest)	3m 49s
Integration tests (windows-latest)	5m 28s
Render tests (windows-latest, 1)	6m 43s
Render tests (windows-latest, 2)	6m 22s
	1h 0m 2s

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