Rename all testdata loading files to conform to a single naming scheme

The scheme is:
- loadBytes: returns a ByteSource of the data
- loadFile: returns a string using UTF8 encoding, optionally applying
  substitutions

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=177606406

javatests/google/registry/flows/domain/DomainTransferQueryFlowTest.java

@@ -53,7 +53,7 @@ public class DomainTransferQueryFlowTest
     eppLoader.replaceAll("JD1234-REP", contact.getRepoId());
     // Setup done; run the test.
     assertTransactionalFlow(false);
-    runFlowAssertResponse(readFile(expectedXmlFilename));
+    runFlowAssertResponse(loadFile(expectedXmlFilename));
     assertAboutDomains().that(domain).hasOneHistoryEntryEachOfTypes(
         HistoryEntry.Type.DOMAIN_CREATE,
         HistoryEntry.Type.DOMAIN_TRANSFER_REQUEST);