### Packages impacted by this PR
N/A
### Issues associated with this PR
N/A
### Describe the problem that is addressed by this PR
Our codespaces setup uses a custom Dockerfile in order to configure docker-in-codespaces and install rush.
But nowadays the default image installs docker by default and we can move installing rush to a post-create-script
instead of building the container.
All-in-all this reduces the time to start by over 50%, avoiding the need to build a custom image every time and reusing the
prebuilt default image. It also reduces the amount of code we have to maintain.
From 1 minute and 7 seconds to 23 seconds before the file tree shows up. I just picked that event arbitrarily.
Resolves#17011
The base image now contains the same logic for installing Docker,
so by the time our custom file ran Docker was already installed which
causes Codespaces creation to error.
This commit does a few things:
1. It restores our ability to use codespaces for development
2. It installs rush globally
3. It disables Oryx's default behavior for node since it conflicts with `rush`
Maor Leger
Jeremy Meng
Mitch Denny