feat(sessions): store session's meatadata

[raoxiaoyan]

Summary

Engineering brief:
https://docs.google.com/document/d/1r7nSZGOlTVhupoVGQ6Ymqsaw64eGHKSMibko8FgrwAQ/edit?tab=t.0
### This PR won't bring a break change.
Add two new configurationshash_subject(by default false) and store_metadata(by default false). Please ref here.
Add a new table session_metadatas to store the session's metadata.

CREATE TABLE IF NOT EXISTS session_metadatas(
        id            uuid,
        session_id    uuid                    REFERENCES "sessions" ("id") ON DELETE CASCADE,
        sid           text,
        subject       text,
        audience      text,
        created_at    timestamp WITH TIME ZONE,
        PRIMARY KEY (id)
      );

Why to do this?
Please check this PR's ticket.

Checklist

• The Pull Request has tests
• A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

KM-788

[raoxiaoyan]

@bungle Could you take a review for this PR, please?

[sumimakito]

The changes in the pull request expose the controls on the hash_subject and store_metadata parameters from lua-resty-session, which look good to me.

[outsinre]

Suggested change

	**session**: Added two configurations `hash_subject` and `store_metadata` to store session's metadata.
	**session**: Added two boolean configuration fields `hash_subject` (default `false`) and `store_metadata` (default `false`) to store session's metadata in the database.

[outsinre]

If the session data is stored in the cookie, should we care about the session metadata?