fix: allow commas and semicolons between fields in constant messages #2065

Job	Run time
Check sync-readme	38s
linux beta (default features)	2m 29s
linux nightly (all features)	1m 57s
linux stable (default features)	2m 35s
linux stable (with-bytes)	1m 12s
mega-linter	2m 8s
rustfmt check	35s
Miri test	44s
CI self-check	5s
windows stable (default features)	4m 25s
	16m 48s

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