testament silently ignores top-level tests

[timotheecour]

testament silently ignores top-level tests, eg tests/trunner.nim was silently ignored (which I'm working around in #14377 by moving it under tests/misc/trunner.nim)

this should be considered a bug, as echoed by @alaviss here #14377 (comment)

Sounds like a bug to me. We should fix this given that testament is now a part of the official Nim distribution.

Example

tests/trunner.nim

Current Output

silently ignored

Expected Output

• (not preferred but better) give an error
• (preferred) run the test, under a special category called "toplevel" (so that testament pcat toplevel works); and give an error if a toplevel dir also exists to avoid clashes

Additional Information

• 40ac195 1.3.5
• test_nimscript.nims is already being tested separately in koch.nim; IIRC only nim files are being tested in testament, so nothing would change for this file; note that we can't make testament test nims files because of config files like tests/newconfig/tfoo.nims which is attached to tests/newconfig/tfoo.nim instead of being a standalone test