galaxy-importer errantly evaluates requires_ansible as semver

The ansible-core project, which is linked to the `requires_ansible` value from `meta/runtime.yml` is validated as semver by the galaxy-importer. However, ansible-core does not use semver for releases currently, which could potentially cause issues, especially if a collection declares a minimum requirement for a beta or rc release of ansible-core

Example:

>=2.12.0b1

In core we use the following code for validating this version:

https://github.com/ansible/ansible/blob/865bda3a11486ea502108381c972b21d91bfe983/lib/ansible/plugins/loader.py#L1132-L1145

Which would require use of `packaging.specifiers.SpecifierSet` instead of `semantic_version.SimpleSpec`