RFE: Support %autochangelog and %autorelease when doing tagless imports using rpmautospec logic

[nazunalika]

CentOS Stream 10 (and Fedora) have rpmautospec as opt-in. This means that release tags can easily have %autorelease and/or %autochangelog.

When processing a repo that has SOURCES and SPECS, this generally isn't a big deal. These are typically in the format we expect with everything filled out.

When processing a repo that has everything in a flat structure, the SPEC file may have %autorelease. This can also mean %autochangelog may exist, which means an accompanying changelog file in the repo will also exist alongside the spec file.

When importing with srpmproc with tagless mode, it should be possible to properly assess the release and changelog and fill them in accordingly.

pv2 currently supports this by importing the rpmautospec python library.

Example starting spec: https://gitlab.com/redhat/centos-stream/rpms/PyYAML/-/blob/c10s/PyYAML.spec
Example processed spec: https://git.rockylinux.org/staging/src-rhel/rpms/pyyaml/-/blob/c10s/SPECS/PyYAML.spec

It should be noted that while %changelog is appended to the spec file, %autorelease is not modified. It is processed by the macro logic added at the top of the spec file by rpmautospec (if applicable). Otherwise, it is processed by other means.