Add Formatting job

Add Formatting job

This change adds the Windows and Ubuntu formatting jobs to the lab, and
makes them requestable. This also enables them to be run on push. The
jobs do the following:

On Windows:

- Build the Checked/Debug/Release builds as usenmakemakefiles, which
  is a configureonly option (so won't do a full build)
- Download the bootstrap script for jitutils
- Download the correct version of dotnet cli
- Run the bootstrap script
- Run jit-format for Windows_NT Checked/Debug/Release
  dll/standalone/crossgen configurations

On Ubuntu:

- Build release, checked, debug builds of coreclr in configureonly mode.
  This will only run cmake and generate the compile_commands.json
- Install the correct version of dotnet cli
- Install the bootstrap script for jitutils
- Run the bootstrap script
- Run jit format over all configurations for Ubuntu (release, checked,
  debug x dll, standalone, crossgen)