Problem:
"tmux 3.2a" (output from "tmux -V") is not parsed easily.
Solution:
With `strict=false`, discard everything before the first digit.
- rename Semver => Version
- rename vim.version.version() => vim.version._version()
- rename matches() => has()
- remove `opts` from cmp()
Problem:
If major<major but minor>minor, cmp_version_core returns 1
Solution:
- Fix logic in cmp_version_core
- Delete most eq()/gt()/lt() tests, they are redundant.
- version.cmp(): assert valid version
- add test for loading vim.version (the other tests use shared.lua in
the test runner)
- reduce test scopes, reword test descriptions
