Bump Java language level to Java 11

Follow up to JGit and Gerrit project, that switched to Java
language level 11.

One side effect of this change is that tools/eclipse/project.sh script
is using bazlets and JavaSE-1.8 is still generated there. In follow up
change Bazlets version will be updated to generate Java 11 compatible
eclipse project.

Change-Id: I488bc6e148e41dfdaef9dcf8b1031df1d22a582d

.bazelrc

diff --git a/.bazelrc b/.bazelrc
index dde54fe..fb5f9d6 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -3,7 +3,7 @@
 build --experimental_strict_action_env
 build --action_env=PATH
 build --disk_cache=~/.gerritcodereview/bazel-cache/cas
-build --java_toolchain //tools:error_prone_warnings_toolchain
+build --java_toolchain //tools:error_prone_warnings_toolchain_java11
 
 test --build_tests_only
 test --test_output=errors