Fix dependency esql -> esql-core

This cannot be compileOnly; otherwise some tests fail because the
SingleValueQuery class cannot be loaded.

x-pack/plugin/esql/build.gradle

@@ -18,7 +18,7 @@ base {
 dependencies {
   compileOnly project(path: xpackModule('core'))
   compileOnly project(':modules:lang-painless:spi')
-  compileOnly project(xpackModule('esql-core'))
+  implementation project(xpackModule('esql-core'))
   implementation project('compute')
   implementation project('compute:ann')
   implementation project(':libs:elasticsearch-dissect')