Support minor release on release branch

[jackye1995]

Since we switched to semantic versioning, we have had 2 major releases and multiple patch releases, things have been stablized and streamlined at this point.

Currently the main problems I see are that:

1. major releases take around 2 weeks to fully pass because of multiple RCs, which slows down development and release in downstream projects
2. minor releases cannot be cut because we frequently have breaking changes that have to bump major

Based on the community sync discussion, I propose that we learn from projects like DataFusion and allow releasing a minor version in a release branch. The new rules are the following:

1. a minor release can be cut from either main or release branch
2. a minor release should only be cut from release branch if the next release in the main branch is going to be a major release
3. similar to any patch commits, feature commits in release branch must also first be committed to main. The newly introduced CodeX Backport PR GitHub workflow can help backporting the feature commits more easily.

Example 1:

Currently we have released version 2.0.0. The main branch is at 2.1.0-beta.1 (no new breaking changes has happened). Then we will just cut 2.1 release from main branch. This would create a release/v2.1 branch rooted from the latest main branch commit.

Example 2:

Currently we have released version 2.0.0. The main branch is at 3.0.0-beta.1 (some new breaking changes has happened). Then if we want a new release before 3.0.0 release, we will backport the PRs needed to release/v2.0 and then cut a 2.1.0 release on release/v2.0. This would create a release/v2.1 branch rooted from the latest release/v2.0 branch commit.

Note that this is a proposal for release process change in lance repo, I don't think it requires a vote, but if we agree on this direction, I will submit a PR around it.

One open question: currently we require 3 day voting period for minor release. If the goal here is to get a stable release out more quickly, would it make more sense to reduce the voting period to something like 1 day? (if we want to change this, it would require a vote in PMC private list since it changes the governance document itself)

[jackye1995]

implementation: #5949