Switch core-tests-support to @CorePlatformApi

Rather than depending on internals, switch core-tests-support
to using the core platform API.

core-tests-support had a static dependency on the platform
bouncycastle target which included a copy of the repackaged
bouncycastle in CTS. This copy would then not be used. This looks
like a mistake. After this change a copy of bouncycastle is included
under its original package.

TestIoUtils was relying on a hidden method in java.lang.Math. This
has been replaced with public API calls.

Bug: 113148576
Test: build
Test: Ran CTS: cts -m CtsLibcoreTestCases
Change-Id: Ib8045537c2c191aca3f416cc459f265c8d957dfc
diff --git a/JavaLibrary.bp b/JavaLibrary.bp
index e187e66..1f312a6 100644
--- a/JavaLibrary.bp
+++ b/JavaLibrary.bp
@@ -334,16 +334,14 @@
     hostdex: true,
     srcs: ["support/src/test/java/**/*.java"],
 
-    no_standard_libs: true,
+    sdk_version: "core_platform_current",
     libs: [
-        "core-all",
         "junit",
-        "bouncycastle",
     ],
-    system_modules: "core-all-system-modules",
     static_libs: [
-        "bouncycastle-bcpkix",
-        "bouncycastle-ocsp",
+        "bouncycastle-unbundled",
+        "bouncycastle-bcpkix-unbundled",
+        "bouncycastle-ocsp-unbundled",
     ],
 }