Refactor regression tests execution in workflow

- Updated [scala.yml] to execute [NaxRiscvRegression] and [NaxRiscvRvls] tests separately using [sbt testOnly].
- Removed [test-regression] and [test-rvls] functions from [tools.sh], as they are now directly handled in the workflow.
- Added environment variables [NAXRISCV_REGRESSION_THREAD_COUNT] and [SBT_OPTS] in the workflow for better resource control and test isolation.

.github/workflows/scala.yml

@@ -62,7 +62,13 @@ jobs:
         run: sbt clean compile
 
       - name: Regression Test SIMULATOR
-        run: source .github/workflows/tools.sh && test-regression
+        run: |
+          export NAXRISCV_REGRESSION_THREAD_COUNT=1
+          export SBT_OPTS="-Xmx2G -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled -XX:MaxPermSize=2G -Xss2M -Duser.timezone=GMT"
+          sbt "testOnly *NaxRiscvRegression"
 
       - name: Regression Test RVLS
-        run: source .github/workflows/tools.sh && test-rvls
+        run: |
+          export NAXRISCV_REGRESSION_THREAD_COUNT=1
+          export SBT_OPTS="-Xmx2G -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled -XX:MaxPermSize=2G -Xss2M -Duser.timezone=GMT"
+          sbt "testOnly *NaxRiscvRvls"

.github/workflows/tools.sh

@@ -83,11 +83,3 @@ install_all(){
   export NAXRISCV=${PWD}
   make install
 }
-
-test-regression(){
-  make test-regression
-}
-
-test-rvls(){
-  make test-rvls
-}