[FEATURE]: Self update on garden cli

Feature Request

It would be really nice to have a self update on the garden cli interface to simplify the update process when a new release comes out

Background / Motivation

I have 20+ guys and gals working with Garden and telling them to use the install script for updating the garden environment every time there is a new release is going to get old really fast and people are going to lag behind. On the other hand to poke them to just run another command on the garden tool they run every day is not that hard

What should the user be able to do?

I envision users pretty much running a command like shown here below to trigger the update. In the short term if this just run the install script from the website to override the current installation, that is fine by me, as long as garden gets updated

garden self-update

Why do they want to do this? What problem does it solve?

• Simplifies updating of CLI
• Makes easier to keep developers up to date

Suggested Implementation(s)

garden self-update

How important is this feature for you/your team?

🌵 Not having this feature makes using Garden painful

[10ko]

Just for posterity, the garden self-update command has been released in Garden 0.12.25.

See docs: https://docs.garden.io/reference/commands#garden-self-update

[ITHedgeHog]

Whilst we have a smaller team, it is one of the barriers to the adoption of garden.io to our process. It would be awesome if it came sooner rather than later.