AGE extension version check

[rhizome-ai]

AGE has no function to show AGE version, so when I need to check the AGE version, I can get it with "select * from pg_extension" statement alternatively.
But, when I upgrade Docker container(to new version of AGE) with external volume mount for data directory(filled with old version data), the extension version of AGE remains old one in pg_extension. It can make confusion to some application developers.
So, I need one of two bellow;

1. A function to show AGE version installed.
2. Check and update version in pg_extension

[deem0n]

This is related to #132 and #156