cli: make tests faster

[2501babe]

cli tests spin up a full test validator for every test case, which takes forever to run as we add more cases. it also runs cases in serial because running many test validators at once is cpu murder. we should be fine spinning up one single validator for all tests, and letting every case create its own rpc client and vote account

i noticed a few weeks ago std has LazyLock now, which is a threadsafe OnceCell, basically like lazy_static. could probably use that

(not a priority, do it if we add more program instructions)

[joncinque]

You can also consider what the token-cli tests do, using a custom test harness with libtest-mimic: https://github.com/solana-program/token-2022/blob/a26984d70b7a5d8e9f8a11615356772bb6454d9a/clients/cli/tests/command.rs#L78