[Transform] finish backport: adapt versions to 7.12 (#67826)

build.gradle

@@ -175,8 +175,8 @@ tasks.register("verifyVersions") {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
-String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/67821" /* place a PR link here when committing bwc changes */
+boolean bwc_tests_enabled = true
+String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
 /*
  * 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/transform/transforms/SourceConfig.java

@@ -97,7 +97,7 @@ public class SourceConfig implements Writeable, ToXContentObject {
     public SourceConfig(final StreamInput in) throws IOException {
         index = in.readStringArray();
         queryConfig = new QueryConfig(in);
-        if (in.getVersion().onOrAfter(Version.V_8_0_0)) {
+        if (in.getVersion().onOrAfter(Version.V_7_12_0)) {
             runtimeMappings = in.readMap();
         } else {
             runtimeMappings = Collections.emptyMap();
@@ -128,7 +128,7 @@ public class SourceConfig implements Writeable, ToXContentObject {
     public void writeTo(StreamOutput out) throws IOException {
         out.writeStringArray(index);
         queryConfig.writeTo(out);
-        if (out.getVersion().onOrAfter(Version.V_8_0_0)) {
+        if (out.getVersion().onOrAfter(Version.V_7_12_0)) {
             out.writeMap(runtimeMappings);
         }
     }