Upgrade to Java 25 (#3000)

Error-prone introduced many more checks in Java 25. We fixed a few
and suppressed most. A follow-up bug is opened to clean this up.
An ai agent should be able to clean up most of it.

This PR is created with gemini-cli. Summary of experience:

* The good: AI caught most compatibility issues, and with permission,
  suppressed them through compiler flags and errorprone options.
  It also caught many versio references in scripts.

* Where it didn't shine:
  - It did not find and update the target version spec in the custome
    VKey annotation processor source file.
  - It did not flag eclipse-temurin:21 docker image for upgrade.
  - When running into failure, its first instinct is to disable checks
    e.g., -Werror instead of fixing them.

java_common.gradle

@@ -71,8 +71,7 @@ configurations {
 }
 
 dependencies {
-    // compatibility with Java 17
-    errorprone("com.google.errorprone:error_prone_core:2.23.0")
+    errorprone("com.google.errorprone:error_prone_core:2.48.0")
 }
 
 test {
@@ -113,14 +112,20 @@ tasks.withType(JavaCompile).configureEach {
   // The -Werror flag causes Intellij to fail on deprecated api use.
   // Allow IDE user to turn off this flag by specifying a Gradle VM
   // option from inside the IDE.
-  if (System.getProperty('no_werror') != 'true') {
+  if (project.hasProperty('no_werror') && project.property('no_werror') == 'true') {
+     // skip -Werror
+  } else if (System.getProperty('no_werror') == 'true') {
+     // skip -Werror
+  } else {
     options.compilerArgs << "-Werror"
   }
   if (name.equals('compileTestJava')) {
     // Allow unused methods in tests.
     options.errorprone.disable("UnusedMethod")
     // Allow unused variables in tests.
-    options.errorprone.disable("UnusedVariable")
+    // TODO(b/498588847): uncomment below when the global suppression
+    // below is removed.
+    // options.errorprone.disable("UnusedVariable")
   }
   // Allow using non-constant strings in log.
   options.errorprone.disable("FloggerLogString")
@@ -134,6 +139,32 @@ tasks.withType(JavaCompile).configureEach {
   options.errorprone.disable("LongDoubleConversion")
   // Allow import of commonly-used names such as "Type".
   options.errorprone.disable("BadImport")
+
+  // TODO(b/498588847): Review suppressed checks below
+  // Disable new checks in 2.48.0 that break the build with -Werror
+  options.errorprone.disable("ExpensiveLenientFormatString")
+  options.errorprone.disable("EnumOrdinal")
+  // Triggered by JapaneseLanguageValidator
+  options.errorprone.disable("ClassInitializationDeadlock")
+  // Allow unused variables globally.
+  options.errorprone.disable("UnusedVariable")
+  options.errorprone.disable("AnnotateFormatMethod")
+  options.errorprone.disable("EffectivelyPrivate")
+  options.errorprone.disable("JdkObsolete")
+  options.errorprone.disable("ImpossibleNullComparison")
+  options.errorprone.disable("UnnecessaryAssignment")
+  options.errorprone.disable("PatternMatchingInstanceof")
+  options.errorprone.disable("IntLiteralCast")
+  options.errorprone.disable("SystemConsoleNull")
+  options.errorprone.disable("FormatStringShouldUsePlaceholders")
+  options.errorprone.disable("BooleanLiteral")
+  options.errorprone.disable("StatementSwitchToExpressionSwitch")
+  options.errorprone.disable("AssignmentExpression")
+  options.errorprone.disable("JavaDurationGetSecondsToToSeconds")
+  options.errorprone.disable("StringConcatToTextBlock")
+  options.errorprone.disable("TruthConstantAsserts")
+  options.errorprone.disable("NullArgumentForNonNullParameter")
+
   options.errorprone.disableWarningsInGeneratedCode = true
   options.errorprone.errorproneArgumentProviders.add([
           asArguments: {