Add a env prune or env update command the the pnpm env

[josh-hemphill]

It's not a huge thing so I figure it didn't warrant opening an issue, but this would save a little time, especially when there's lots of security fixes and the like resulting in lots of minor versions of Node. It's nice I can just pnpm env add -g lts latest 18, but then I have to clean up the old ones by listing then deleting them. Having a command to either remove old versions that aren't in some list would be nice, or even better, a command to automatically pull the updated versions based off a provided pattern, like pnpm env upgrade lts latest 18 could detect versions previously in those major versions and remove them and pull down the latest.