Fix eclipse compilation after plugin spi (#76437)

Painless extensions now compile against it's `spi` subproject. Gradle
and IntelliJ rig the dependencies correctly but Eclipse doesn't seem to
manage it. This temporarily declares the `spi` as a `compileOnly`
dependency when in Eclipse land so Eclipse can see the classes.

Author: nik9000

modules/lang-painless/build.gradle

@@ -26,6 +26,10 @@ testClusters.all {
 configurations {
   spi
   compileOnlyApi.extendsFrom(spi)
+  if (isEclipse) {
+    // Eclipse buildship doesn't know about compileOnlyApi
+    api.extendsFrom(spi)
+  }
 }
 
 dependencies {