Offer baseline `RavenwoodFlagsValueProvider`.

Many test authors are starting to use `CheckFlagsRule` across suites
like CTS, so instead of recommending that they use `null` when on
Ravenwood, offer them a clear behavior that is either "all-on" or
"all-off".

Eventually we'll explore providing default flag values on Ravenwood,
but let's get something cleaner available now.

Bug: 318841620
Test: ./frameworks/base/ravenwood/run-ravenwood-tests.sh
Change-Id: Id234a375426fad38f64d3a999339bb720eae84bf
diff --git a/Ravenwood.bp b/Ravenwood.bp
index 4791640..f43c37b 100644
--- a/Ravenwood.bp
+++ b/Ravenwood.bp
@@ -205,8 +205,10 @@
         // Provide runtime versions of utils linked in below
         "junit",
         "truth",
+        "flag-junit",
         "ravenwood-framework",
         "ravenwood-junit-impl",
+        "ravenwood-junit-impl-flag",
         "mockito-ravenwood-prebuilt",
         "inline-mockito-ravenwood-prebuilt",
     ],
@@ -220,6 +222,7 @@
     libs: [
         "junit",
         "truth",
+        "flag-junit",
         "ravenwood-framework",
         "ravenwood-junit",
         "mockito-ravenwood-prebuilt",