refactor(test2): Don't create a type per test

[epage]

No description provided.

[epage]

Well, that is annoying. This doesn't work with our MSRV

  error[E0493]: destructor of `FnCase<{closure@/home/runner/work/libtest2/libtest2/crates/libtest2/src/macros.rs:38:21: 38:30}>` cannot be evaluated at compile-time
    --> crates/libtest2/examples/simple.rs:10:1
     |
  10 | #[libtest2::test]
     | ^^^^^^^^^^^^^^^^^
     | |
     | the destructor for this type cannot be evaluated in statics
     | value is dropped here
     |
     = note: this error originates in the macro `::libtest2::_private::test_parse` which comes from the expansion of the attribute macro `libtest2::test` (in Nightly builds, run with -Z macro-backtrace for more info)

[coveralls]

Pull Request Test Coverage Report for Build 18956108775

Details

• 0 of 21 (0.0%) changed or added relevant lines in 2 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.3%) to 30.203%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/libtest2/src/case.rs	0	1	0.0%
crates/libtest2-harness/src/case.rs	0	20	0.0%

Files with Coverage Reduction	New Missed Lines	%
crates/libtest2/src/case.rs	2	0.0%

Totals
Change from base Build 18943070888:	-0.3%
Covered Lines:	505
Relevant Lines:	1672

---

💛 - Coveralls