bp2build converts java_version property to javacopts attribute

This CL also converts `external/rappor` (which already set `java_version` to `1.7`) to be bazelable to testify the changes.

Results from `b build //external/rappor && cat bazel-bin/external/rappor/librappor.jar-0.params`: https://paste.googleplex.com/5518725462622208.

Test: go test ./bp2build/...
Bug: 227618664
Change-Id: I8d370d4639f70fba51e6de6ceb7bcb5ace9ccd91
diff --git a/android/allowlists/allowlists.go b/android/allowlists/allowlists.go
index 26cfd57..28dc8b4 100644
--- a/android/allowlists/allowlists.go
+++ b/android/allowlists/allowlists.go
@@ -104,12 +104,14 @@
 		"external/google-benchmark":                          Bp2BuildDefaultTrueRecursively,
 		"external/googletest":                                Bp2BuildDefaultTrueRecursively,
 		"external/gwp_asan":                                  Bp2BuildDefaultTrueRecursively,
+		"external/hamcrest":                                  Bp2BuildDefaultTrueRecursively,
 		"external/icu":                                       Bp2BuildDefaultTrueRecursively,
 		"external/icu/android_icu4j":                         Bp2BuildDefaultFalse, // java rules incomplete
 		"external/icu/icu4j":                                 Bp2BuildDefaultFalse, // java rules incomplete
 		"external/javapoet":                                  Bp2BuildDefaultTrueRecursively,
 		"external/jemalloc_new":                              Bp2BuildDefaultTrueRecursively,
 		"external/jsoncpp":                                   Bp2BuildDefaultTrueRecursively,
+		"external/junit":                                     Bp2BuildDefaultTrueRecursively,
 		"external/libcap":                                    Bp2BuildDefaultTrueRecursively,
 		"external/libcxx":                                    Bp2BuildDefaultTrueRecursively,
 		"external/libcxxabi":                                 Bp2BuildDefaultTrueRecursively,
@@ -122,6 +124,7 @@
 		"external/pcre":                                      Bp2BuildDefaultTrueRecursively,
 		"external/protobuf":                                  Bp2BuildDefaultTrueRecursively,
 		"external/python/six":                                Bp2BuildDefaultTrueRecursively,
+		"external/rappor":                                    Bp2BuildDefaultTrueRecursively,
 		"external/scudo":                                     Bp2BuildDefaultTrueRecursively,
 		"external/selinux/libselinux":                        Bp2BuildDefaultTrueRecursively,
 		"external/selinux/libsepol":                          Bp2BuildDefaultTrueRecursively,