So that if a src/ change is made it doesn't do an npm install again.

So that if a backend part is changed, then the frontend image is
not rebuilt and vice versa.

Mainly for the new nodejs 16 LTS, but also pg 14, and linux LTS.

So that only the required deps to build are installed before
building the docker image.

frontend: Move some deps out of devDependencies because the
build depends on them.

Some dependency updates caused the snapshot changes.

The sagas type updates seem to have a problem with cancelled().

icu-data package is used to support better locale formatting.

Alpine 3.13.x comes with Nodejs 14.x which has plenty of improvements,
but one area it improves greatly is locale based formatting.

We were creating the plugins folder if it didn't exist and moving it,
but we need it to exist regardless of whether we have plugins, so this
patch moves the creation after the move (and ensures the move doesn't
fail).

Copying the plugins was failing if the plugins folder was empty, because
in the Dockerfile we tried to copy from /headlamp/plugins but we first
had moved any plugins folder to plugins-old and if the folder was empty,
then the copy command wouldn't create the final plugins directory again.

Fixing that just required creating the mentioned plugins folder after
the move, but there was also the problem that the copy command was
copying everything in each plugins folder and not just the main.js file.

These are the folders we use for the default plugin-dir:

  - the passed in pluginDir if it's not empty.
  - "./.plugins" if it exists.
  - ~/.config/Headlamp/plugins exists or it can be made
  - "./.plugins" if the ~/.config/Headlamp/plugins can't be made.

The user data config path is platform specific, so is different
on Windows for example.

For backwards compatibility, the Dockerfile now copies plugins
from the "./plugins" folder if they match the pattern
plugins/MyFolder/main.js. There is a new plugins folder coming to
the repo, so the .plugins folder is a new place to store built
plugins to be used for deployment.

We should include any plugins we want to ship in the image. So, in order
to do that, this patch copies anything in a local plugins folder into
the image and configures the Kubernetes deployment to use this plugins
dir. If the folder doesn't exist, then no plugins will be loaded by the
backend anyway.

In the future we should validate whether the plugins dir has contents
that resemble the plugins (plugins/*/main.js).

We have an official name now, so this patch adds the respective changes
to the frontend.

These changes add a dockerfile and a makefile target for building a
Docker image.