Gluster Release cadence and version changes

[Shyam Ranganathan]

This announcement is to publish changes to the upstream release cadence
from quarterly (every 3 months), to every 4 months and to have all
releases maintained (no more LTM/STM releases), based on the maintenance
and EOL schedules for the same.

Further, it is to start numbering releases with just a MAJOR version
rather than a "x.y.z" format that we currently employ.

1. Release cadence (Major releases)
- Release every 4 months
- Makes up 3 releases each year
- Each release is maintained till n+3 is released (IOW, for a year, and
n is the release version, thus retaining EOL time for a release as it
stands currently)
- Retain backward compatibility across releases, for ease of
migrations/upgrades

2. Update releases (minor update release containing bug fixes against a
major release)
- First 3 update releases will be done every month
- Further update releases will be made once every 2 months till EOL of
the major release
- Out of band releases for critical issues or vulnerabilities will be
done on demand

3. Release versions
- Releases will be version-ed using a monotonic increasing number
starting at 5
    - Hence future releases would be, release-5, release-6, and so on
- Use minor numbers for update releases, like 5.x or 6.x, x
monotonically increasing every update
- RPM versions would look like <package>.<VERSION.x>-<BUILD>.<DISTRO>.<ARCH>

4. Note on op-version
- op-versions were tied to release versions, and may undergo a change in
description to make it release agnostic

Expect the Gluster release web page to undergo an update within a week.
( https://www.gluster.org/release-schedule/ )

Thanks,
Shyam