testament: use spec tags (more flexible than file hierarchies / dir category)

[timotheecour]

File hierarchies don't convey fact that a given file (eg tests/untestable/thttpclient_ssl_disabled.nim) can be associated with different categories, in this case: integration, ssl, networking, etc.

Instead it's much better to rely on tags, and testament spec is a natural fit for that, eg:

discard """
  targets: "c cpp"
  tags: "integration, ssl, benchmark, networking"
"""

benefits

• This also allows adding/removing/editing tags for a file without having to move files around and loose much of git history in the process.

• Tags would also offer better filtering, eg allowing one to run all tests with tags js and benchmark but not networking: testament --tags:"js,benchmark,-networking"

example tags

• networking
• benchmarking
• integration
• flaky
• windows
• ssl
• parser
• all existing categories (ie the 1st-level directory under tests, eg ccgbugs for tests/ccgbugs/mymodule.nim) are implicit tags
  etc

notes

• tags would be checked by testament against a list to avoid mistyped tags

links

• https://dev.to/moigagoo/comment/1aa4a