fix(toolchain)!: restrict named toolchain characters #4861

Job	Run time
build-macos-aarch64 (dev, aarch64-apple-darwin)	15m 29s
check	49s
doc	5s
build-all-features (ubuntu-latest, x86_64-unknown-linux-gnu)	4m 53s
build-macos-x86_64 (release, x86_64-apple-darwin)	4m 16s
build-all-features (windows-latest, x86_64-pc-windows-msvc)	9m 57s
build-macos-aarch64 (release, aarch64-apple-darwin)	6m 15s
build-macos-x86_64 (dev, x86_64-apple-darwin)	15m 56s
build-windows-pr (dev, aarch64-pc-windows-msvc)	12m 10s
build-windows-pr (dev, x86_64-pc-windows-gnu)	2m 17s
build-windows-pr (release, x86_64-pc-windows-msvc)	4m 19s
build-linux-pr (release, aarch64-unknown-linux-gnu)	3m 11s
build-linux-pr (release, aarch64-linux-android)	2m 57s
build-windows-pr (release, aarch64-pc-windows-msvc)	3m 48s
build-windows-pr (release, aarch64-pc-windows-gnullvm)	4m 16s
build-linux-pr (dev, armv7-unknown-linux-gnueabihf)	1m 23s
build-linux-pr (release, x86_64-unknown-linux-gnu)	2m 43s
build-linux-pr (dev, aarch64-linux-android)	1m 18s
build-linux-pr (dev, x86_64-unknown-linux-gnu)	9m 3s
build-windows-pr (release, x86_64-pc-windows-gnu)	4m 40s
build-linux-pr (dev, aarch64-unknown-linux-gnu)	9m 5s
build-linux-pr (release, armv7-unknown-linux-gnueabihf)	2m 39s
build-windows-pr (dev, x86_64-pc-windows-msvc)	9m 25s
build-windows-pr (dev, aarch64-pc-windows-gnullvm)	3m 11s
build-linux-main	0s
build-linux-stable	0s
build-windows-stable	0s
build-freebsd-stable	0s
build-freebsd-main	0s
build-windows-main	-6s
conclusion	3s
	2h 14m 2s

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