Improve bundle versioning using VERSION file

[frobware]

Move version information into a standalone VERSION file to provide a clear, central source of truth for the project version and future runtime consumers (e.g. CLI programs that may support a --version flag).

There's nothing inherently wrong with the previous approach of hard-coding VERSION in the Makefile. The real issue is that we had no process for bumping the version immediately after a release tag was cut. As a result, subsequent development continued to build and push bundle and catalog images using the same version tag.

For example, once we had tagged 0.5.6, any further updates to the bundle--such as updated manifests--were still pushed to bpfman-operator-bundle:v0.5.6. This isn't expected behaviour and violates the assumption that tagged images are stable and immutable.

The new process for bumping to the next development release:

1. Prepare a release:

   • Update the VERSION file to remove the -dev suffix (e.g. change 0.5.7-dev -> 0.5.7).
   • Run make bundle to generate release manifests with the correct version embedded.
   • Commit both the VERSION and regenerated bundle content.
   • Raise a PR After merging
   • git tag -a the resulting commit (e.g. v0.5.7)

2. Begin the next development cycle:

   • Update the VERSION file to the next dev version (e.g. 0.5.8-dev).
   • Run make bundle again to update the ClusterServiceVersion accordingly.
   • Commit both the VERSION and regenerated bundle content.
   • Raise a PR.

[frobware]

/hold

[frobware]

/hold cancel

[dave-tucker]

@frobware changes LGTM.

However, you should also update the documentation over at https://github.com/bpfman/bpfman/blob/main/RELEASE.md

There's also an argument to be made for potentially splitting that doc into two since we've moved the operator into it's own repository.

We may as well follow the same versioning scheme for bpfman too to avoid drift (i.e bpfman 0.5.6 and bpfman-operator 0.5.7-dev)