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/flows/host/HostInfoFlow.java

@@ -32,7 +32,6 @@ import google.registry.model.domain.DomainBase;
 import google.registry.model.eppcommon.StatusValue;
 import google.registry.model.eppoutput.EppResponse;
 import google.registry.model.host.HostInfoData;
-import google.registry.model.host.HostInfoData.Builder;
 import google.registry.model.host.HostResource;
 import google.registry.model.reporting.IcannReportingTypes.ActivityReportField;
 import google.registry.util.Clock;
@@ -72,7 +71,7 @@ public final class HostInfoFlow implements Flow {
     if (isLinked(Key.create(host), now)) {
       statusValues.add(StatusValue.LINKED);
     }
-    Builder hostInfoDataBuilder = HostInfoData.newBuilder();
+    HostInfoData.Builder hostInfoDataBuilder = HostInfoData.newBuilder();
     // Hosts transfer with their superordinate domains, so for hosts with a superordinate domain,
     // the client id, last transfer time, and pending transfer status need to be read off of it. If
     // there is no superordinate domain, the host's own values for these fields will be correct.