Adjust BWC version for compressing async search response (#74882)

Relates #74766

build.gradle

@@ -144,9 +144,9 @@ tasks.register("verifyVersions") {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
+boolean bwc_tests_enabled = true
 // place a PR link here when committing bwc changes:
-String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/74804"
+String bwc_tests_disabled_issue = ""
 /*
  * FIPS 140-2 behavior was fixed in 7.11.0. Before that there is no way to run elasticsearch in a
  * JVM that is properly configured to be in fips mode with BCFIPS. For now we need to disable

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/async/AsyncTaskIndexService.java

@@ -592,7 +592,7 @@ public final class AsyncTaskIndexService<R extends AsyncResponse<R>> {
         };
         final Version minNodeVersion = clusterService.state().nodes().getMinNodeVersion();
         Version.writeVersion(minNodeVersion, new OutputStreamStreamOutput(os));
-        if (minNodeVersion.onOrAfter(Version.V_8_0_0)) {
+        if (minNodeVersion.onOrAfter(Version.V_7_15_0)) {
             os = CompressorFactory.COMPRESSOR.threadLocalOutputStream(os);
         }
         try (OutputStreamStreamOutput out = new OutputStreamStreamOutput(os)) {
@@ -617,7 +617,7 @@ public final class AsyncTaskIndexService<R extends AsyncResponse<R>> {
         });
         final Version version = Version.readVersion(new InputStreamStreamInput(encodedIn));
         assert version.onOrBefore(Version.CURRENT) : version + " >= " + Version.CURRENT;
-        if (version.onOrAfter(Version.V_8_0_0)) {
+        if (version.onOrAfter(Version.V_7_15_0)) {
             encodedIn = CompressorFactory.COMPRESSOR.threadLocalInputStream(encodedIn);
         }
         try (StreamInput in = new NamedWriteableAwareStreamInput(new InputStreamStreamInput(encodedIn), registry)) {