Fix various Error Prone errors that were found by the FOSS build

Most common:
- Unnecessary parentheses and operator precedence clarify (self-explanatory)
- Reference equality--there were a few instances of using == or != improperly
- Qualification of Builder (and similar) imports so that it's clear which type of Builder we're referring to
- Marking some immutable classes with @Immutable since EP desires that all enums be deeply immutable
- String.split() having "surprising behavior"

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=230971531

java/google/registry/whois/WhoisModule.java

@@ -41,6 +41,7 @@ import javax.servlet.http.HttpServletRequest;
 public final class WhoisModule {
 
   @Provides
+  @SuppressWarnings("CloseableProvides")
   static Reader provideHttpInputReader(HttpServletRequest req) {
     try {
       return req.getReader();