Per changes requested

- build-extra-tests composite-action comment changed to Builds extra test required for FireSim tests
- removed unneeded inputs tools-version and group-key from run-tests composite action
- Added better comment to toolchain-build composite action
- Change CI_MAKE_NPROC back to 8 in defaults.sh
- Moved all the duplicated enviroment setting stuff in workflow file to the top
  - BUILDSERVER, BUILDUSER, CI_DIR, SERVER, and JVM_OPTS
- Romoved all the not needed passed parameters in the calls to run-script
- A bit of cleanup to .github/README.md
  - added link to SO `if` hack
  - cleaned up comments on CI_DIR
  - removed bad empty final bullet line

.github/actions/run-tests/action.yml

@@ -2,13 +2,6 @@ name: run-tests
 description: 'Runs tests according to input parameters'
 
 inputs:
-  tools-version:
-    description: Which toolchain to build
-    required: false
-    default: 'riscv-tools'
-  group-key:
-    description: group key
-    required: true
   project-key:
     description: project key
     required: true