ci: use a matrix for test configurations #1776

Job	Run time
Check docs	27s
Format	21s
Check	48s
Build	1m 18s
Clippy	1m 27s
Run Hermit for Rust (x86_64 + kvm)	4m 51s
Run Hermit for Rust (x86_64, --dev, rusty_demo)	5m 6s
Test	1m 13s
Run Hermit for Rust (x86_64, --dev, httpd)	3m 29s
Run Hermit for Rust (x86_64, --dev, httpd-rtl8139)	4m 16s
Run Hermit for Rust (x86_64, --dev, testudp)	3m 16s
Run Hermit for Rust (x86_64, --dev, microvm)	2m 43s
Run Hermit for Rust (x86_64, --release, rusty_demo)	5m 10s
Run Hermit for Rust (x86_64, --release, httpd)	3m 18s
Run Hermit for Rust (x86_64, --release, httpd-rtl8139)	3m 2s
Run Hermit for Rust (x86_64, --release, testudp)	3m 6s
Run Hermit for Rust (x86_64, --release, microvm)	2m 49s
Run Hermit for Rust (aarch64, --dev, rusty_demo)	4m 13s
Run Hermit for Rust (aarch64, --dev, httpd)	3m 24s
Run Hermit for Rust (aarch64, --dev, testudp)	3m 21s
Run Hermit for Rust (aarch64, --release, rusty_demo)	4m 41s
Run Hermit for Rust (aarch64, --release, httpd)	4m 15s
Run Hermit for Rust (aarch64, --release, testudp)	3m 49s
	1h 10m 23s

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