Alcotezt UX improvements

The Alcotezt project has incurred some usability regressions on unit test execution.

Problems

Notably, it is no longer possible, or hard to:

• (A) Select all tests in a specific folder / package / file
• (B) Selecting sub-tests: we now group tests at a coarser-grain, which makes it harder to selected individual cases.
  • In alcotest, a "test suite" is a sequence of "tests" that are composed of a sequence of "test cases".
  • In tezt, there is only "tests" that are loosely grouped by "files" and horizontally by "tags".
  • With alcotezt, we group each alcotest "test" into a tezt "test". consequently, we can no longer execute individual test cases.
• (C) Invocation headers
  • Test files have traditionally contained a "test header", as described here: https://tezos.gitlab.io/developer/testing.html#conventions, including an invocation header.
  • During the project, we've broken most of the invocation headers. Here's an example of a broken header: https://gitlab.com/tezos/tezos/blob/master/src/proto_016_PtMumbai/lib_client/test/test_client_proto_context.ml#L29
• (D) Understanding where a failing test in the CI is located
• (E) Having both runtest and runtezt is confusing

Constraints on solution

• opam tests must continue to work
• runtest/runtezt should work
• tezt entrypoint should work
• tezt --list should give legible output

Proposed solutions

• Problem A / D.
  • Modify Tezt's --match to match on file names (tags?)? (MR: nomadic-labs/tezt!17 (merged))
  • Modify Tezt's --file so that it can match basenames or full paths (MR: nomadic-labs/tezt!13 (merged))
  • Adding ~__FILE__ to Alcotest(_lwt).run (MR: !7965 (merged))
  • Adding tags to protocol tests and cleaning up their titles (!8109 (closed), !8390 (merged))
  • The above fixes will also solve problem D: when tests will be registered by full path that path will appear in error messages.
• Problem B.
  • Experiment with splitting tests (!8227 (merged) and !8228 (merged))
• Problem C.
  • Fixing broken invocation headers: (in progress: #5172 (closed)). This makes the headers work, but more imprecise.
  • Shorten test titles, and updating invocations headers to make them more precise (!8408 (merged), !8400 (merged))
• Problem E.
  • Merging runtezt into runtest (!7968 (closed) and !8502 (merged))