Use mermaid for migrations graph #4580

Job	Run time
Bitrot check	3m 54s
Test on ubuntu-latest	12m 17s
Test on ubuntu-latest with --features orchard	12m 24s
Test on ubuntu-latest with --features unstable-nu6	12m 33s
Clippy (MSRV)	4m 8s
Build target wasm32-wasi	3m 41s
Test on ubuntu-latest with --features zfuture	12m 17s
Latest build on ubuntu-latest	1m 51s
Test on windows-latest	16m 55s
Latest build on windows-latest	4m 15s
Clippy (beta)	13s
Test on windows-latest with --features orchard	17m 10s
Code coverage	19m 49s
Latest build on macOS-latest	2m 31s
Test on windows-latest with --features unstable-nu6	16m 58s
Intra-doc links	4m 39s
Rustfmt	12s
Test on windows-latest with --features zfuture	17m 6s
protobuf consistency	3m 58s
Test on macOS-latest	15m 30s
UUID validity	3s
Test on macOS-latest with --features orchard	19m 6s
	3h 21m 30s

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