fix(datastore): update emulator zip checksum for 2.3.1 (#14592)

Fixes #12058.

`LocalDatastoreHelper` still hands `e0d1170519cf52e2e5f9f93892cdf70c` to
`DownloadableEmulatorRunner`, and that is the checksum of the *2.0.2*
archive, not the 2.3.1 one it now points at. Found the culprit while
going through the file history: `e17b57b6` moved `MIN_VERSION` to 2.0.2
and set the checksum that matched, then `9eb86f06` (#1698) moved
`MIN_VERSION` on to 2.3.1 and didn't bring the checksum along. `curl -I`
on the old zip still reports `ETag: e0d1170519cf52e2e5f9f93892cdf70c`,
which is how I spotted it.

Since `downloadZipFile()` compares the two and re-fetches on mismatch,
the condition was true on every call and each `start()` pulled ~36 MB
again even with a perfectly good copy sitting in `java.io.tmpdir`.

Verified against the real artifact rather than just eyeballing the
string. The 2.3.1 zip is 37,929,131 bytes; downloading it and running
`md5sum` gives `7c1f5a3276241a8f78cb1a837daaaa47`, and GCS agrees
(`ETag` plus the `x-goog-hash` md5, base64 `fB9aMnYkGo94yxqDfaqqRw==`).
I also replayed the check from `BaseEmulatorHelper` over the downloaded
file: the old constant makes it re-download, the new one lets it use the
cached copy.

The second commit is a separate small thing I ran into in the same
constructor, so it's easy to drop if you'd rather keep this to one
change: the gcloud command line is built from the raw
`builder.consistency` while the downloadable runner's uses
`getConsistency()`. `newBuilder().build()` leaves `builder.consistency`
at 0.0 while `getConsistency()` resolves to `DEFAULT_CONSISTENCY` (0.9),
so the two runners disagree for the same helper. Using
`getConsistency()` in both makes them match.

---------

Co-authored-by: rootkiller6788 <rootkiller6788@users.noreply.github.com>

Author: rootkiller6788

java-datastore/google-cloud-datastore/src/main/java/com/google/cloud/datastore/testing/LocalDatastoreHelper.java

@@ -65,7 +65,7 @@ public class LocalDatastoreHelper extends BaseEmulatorHelper<DatastoreOptions> {
   // Downloadable emulator settings
   private static final String BIN_NAME = "cloud-datastore-emulator/cloud_datastore_emulator";
   private static final String FILENAME = "cloud-datastore-emulator-" + MIN_VERSION + ".zip";
-  private static final String MD5_CHECKSUM = "e0d1170519cf52e2e5f9f93892cdf70c";
+  private static final String MD5_CHECKSUM = "7c1f5a3276241a8f78cb1a837daaaa47";
   private static final String BIN_CMD_PORT_FLAG = "--port=";
   private static final URL EMULATOR_URL;
   private static final String EMULATOR_URL_ENV_VAR = "DATASTORE_EMULATOR_URL";
@@ -176,7 +176,7 @@ private LocalDatastoreHelper(Builder builder) {
     } else {
       // At most one of --consistency | --use-firestore-in-datastore-mode can be specified.
       // --consistency will be ignored with --use-firestore-in-datastore-mode.
-      gcloudCommand.add(CONSISTENCY_FLAG + builder.consistency);
+      gcloudCommand.add(CONSISTENCY_FLAG + getConsistency());
     }
     if (!builder.storeOnDisk) {
       gcloudCommand.add("--no-store-on-disk");