Allow non-semver packages in the Conan package registry (#20412) (#20523)

Allow non-semver packages in the Conan package registry (#20412) (#20523)

Backport #20412

A lot of existing packages do not conform to SemVer, yet, they should be allowed
in the Conan package registry as-is. To achieve this, remove the SemVer check
from `NewRecipeReference`, and replace it with a simple empty string check.

A unit test with a non-semver version is also included.

Fixes #20405.

Signed-off-by: Gergely Nagy <me@gergo.csillger.hu>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: Gergely Nagy <algernon@users.noreply.github.com>