Bump minimum Java version to 17 and add Java 21 build

Change-Id: Ia063d5de28cd69152286a3dec4a6f614f1549915

.bazelrc

diff --git a/.bazelrc b/.bazelrc
index 7c7def3..4e6427a 100644
--- a/.bazelrc
+++ b/.bazelrc
@@ -8,17 +8,17 @@
 build --action_env=PATH
 build --disk_cache=~/.gerritcodereview/bazel-cache/cas
 
-# Builds using remote_jdk11, executes using remote_jdk11 or local_jdk
-build --java_language_version=11
-build --java_runtime_version=remotejdk_11
-build --tool_java_language_version=11
-build --tool_java_runtime_version=remotejdk_11
-
 # Builds using remote_jdk17, executes using remote_jdk17 or local_jdk
-build:java17 --java_language_version=17
-build:java17 --java_runtime_version=remotejdk_17
-build:java17 --tool_java_language_version=17
-build:java17 --tool_java_runtime_version=remotejdk_17
+build --java_language_version=17
+build --java_runtime_version=remotejdk_17
+build --tool_java_language_version=17
+build --tool_java_runtime_version=remotejdk_17
+
+# Builds using remote_jdk21, executes using remote_jdk21 or local_jdk
+build:java21 --java_language_version=21
+build:java21 --java_runtime_version=remotejdk_21
+build:java21 --tool_java_language_version=21
+build:java21 --tool_java_runtime_version=remotejdk_21
 
 test --build_tests_only
 test --test_output=errors