synth-bm: include it in the root workspace #10101

Job	Run time
Cargo Nextest (Linux)	11m 5s
Backward Compatibility	11m 12s
Cargo Nextest (Linux Nightly)	10m 58s
Protobuf Backward Compatibility	13s
Sanity Checks	6m 35s
Database Migration	11m 56s
Cargo Fmt	22s
Protocol Schema	13m 48s
Style	35s
Genesis Changes	10m 22s
Upgradability	11m 48s
Cargo Audit	21s
Cargo Deny	34s
Cargo Clippy	9m 12s
Non-default Configuration Builds	1m 14s
Themis	42s
Unused Dependencies	6m 59s
Rust Doctests	11m 10s
spellcheck	22s
Cargo check publishable packages separately (Linux, linux, ubuntu-latest)	9m 39s
Cargo check publishable packages separately (Windows, win, windows-latest)	3m 20s
Generate Coverage Artifact (unit, unit)	2m 30s
Upload Coverage	21s
	2h 15m 18s

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