Release notes should be version agnostic

[tisonkun]

Currently, we host release notes under docs/v0.7/en/release-notes.

This is not scalable, because we should not copy the whole release note folder to docs/v0.8/en when v0.8 is cut.

Instead, we should make the release notes version agnostic. Here are two possible ways:

1. Lift the release-notes folder and set symbol link at each version directory, use the summary.yml to control which range of release notes should be displayed.

This is easy to implement, but our pre-commit is unhappy with this:

> greptime_docs@1.0.0 lint-staged /Users/tison/GreptimeWorkspace/docs
> npx lint-staged

✖ error: 'docs/v0.7/en/release-notes/all-releases.md' is beyond a symbolic link
  fatal: Unable to process path docs/v0.7/en/release-notes/all-releases.md
  Cannot save the current worktree state

Related to lint-staged/lint-staged#1318.

2. Copy the files on build, or use branches for each version.

This is how pingcap/docs works - one branch for a version. It may require more complex build set up.

What do you think? @GreptimeTeam/marketing @nicecui @Aganivi @alili