Restructure CI with matrix approach and multi-feature support (#7376)

* `--features` flag can take multiple values

* Simplify CI job

* Remove bad default

* Enable jit on macOS

scripts/whats_left.py

@@ -67,9 +67,9 @@ def parse_args():
     )
     parser.add_argument(
         "--features",
-        action="store",
-        help="which features to enable when building RustPython (default: ssl)",
-        default="ssl",
+        action="append",
+        help="which features to enable when building RustPython (default: [])",
+        default=[],
     )
 
     args = parser.parse_args()
@@ -449,16 +449,20 @@ with open(GENERATED_FILE, "w", encoding="utf-8") as f:
 cargo_build_command = ["cargo", "build", "--release"]
 if args.no_default_features:
     cargo_build_command.append("--no-default-features")
+
+joined_features = ",".join(args.features)
 if args.features:
-    cargo_build_command.extend(["--features", args.features])
+    cargo_build_command.extend(["--features", joined_features])
 
 subprocess.run(cargo_build_command, check=True)
 
 cargo_run_command = ["cargo", "run", "--release"]
 if args.no_default_features:
     cargo_run_command.append("--no-default-features")
+
 if args.features:
-    cargo_run_command.extend(["--features", args.features])
+    cargo_run_command.extend(["--features", joined_features])
+
 cargo_run_command.extend(["-q", "--", GENERATED_FILE])
 
 result = subprocess.run(