refactor scalac deps

Refactor SCALAC_DEPS parameter to a Starlark file to make it reusable for
users.

See #1674 for a possible usecase.

Author: gergelyfabian

src/java/io/bazel/rulesscala/scalac/BUILD

@@ -1,17 +1,7 @@
-load("@rules_java//java:defs.bzl", "java_binary")
 load("@io_bazel_rules_scala_config//:config.bzl", "ENABLE_COMPILER_DEPENDENCY_TRACKING")
+load("@rules_java//java:defs.bzl", "java_binary")
 load("//scala:scala_cross_version_select.bzl", "select_for_scala_version")
-
-SCALAC_DEPS = [
-    "//scala/private/toolchain_deps:scala_compile_classpath",
-    "//src/java/io/bazel/rulesscala/io_utils",
-    "@bazel_tools//src/main/protobuf:worker_protocol_java_proto",
-    "@io_bazel_rules_scala//src/java/io/bazel/rulesscala/jar",
-    "@io_bazel_rules_scala//src/java/io/bazel/rulesscala/worker",
-    "@io_bazel_rules_scala//src/protobuf/io/bazel/rules_scala:diagnostics_java_proto",
-    "//src/java/io/bazel/rulesscala/scalac/compileoptions",
-    "//src/java/io/bazel/rulesscala/scalac/reporter",
-]
+load("//src/java/io/bazel/rulesscala/scalac:deps.bzl", "SCALAC_DEPS")
 
 java_binary(
     name = "scalac",
@@ -48,8 +38,8 @@ java_binary(
 filegroup(
     name = "scalac_files",
     srcs = [
-        "ScalacWorker.java",
         "ScalacInvokerResults.java",
+        "ScalacWorker.java",
     ] + select_for_scala_version(
         any_2 = glob(["scala_2/*.java"]),
         any_3 = glob(["scala_3/*.java"]),

src/java/io/bazel/rulesscala/scalac/deps.bzl

@@ -0,0 +1,10 @@
+SCALAC_DEPS = [
+    "//scala/private/toolchain_deps:scala_compile_classpath",
+    "//src/java/io/bazel/rulesscala/io_utils",
+    "@bazel_tools//src/main/protobuf:worker_protocol_java_proto",
+    "@io_bazel_rules_scala//src/java/io/bazel/rulesscala/jar",
+    "@io_bazel_rules_scala//src/java/io/bazel/rulesscala/worker",
+    "@io_bazel_rules_scala//src/protobuf/io/bazel/rules_scala:diagnostics_java_proto",
+    "//src/java/io/bazel/rulesscala/scalac/compileoptions",
+    "//src/java/io/bazel/rulesscala/scalac/reporter",
+]