new spinners and UI for forge test, see also Cargo (status logs like "checking"), cargo-nextest spinner and streaming test output

• we don't group per "test suite" (contract), they're just like an extra separator like in Rust tests (crate::mod_a::mod_b::test_name)
• main thread handles individual test events instead of just test results
  • keeps a buffer of currently running tests with a spinner for each, and a general spinner with counter for all the tests
  • events include test start, fuzz/invariant update counter, and test result, keyed by ID
  • once a test is done, the spinner line is replaced with the pass/fail result, logs, traces etc