Refactor CrossProjectIndexExpressionsRewriter (#135588)

Refactoring pass over `CrossProjectIndexExpressionsRewriter` to make it
plug into the end-to-end expression rewriting flow
(#135346).

The main change is isolating the logic of rewriting a single expression
into `rewriteIndexExpression`. Also, fixes two smaller quirks:

- instead of rewriting an empty index expression to `"*"` we rewrite to `_all`. There is a marginal difference in behavior between the two and `_all` better matches empty index expression behavior
- uses project aliases consistently across rewriting qualified and unqualified expressions

Author: n1v0lg

server/src/main/java/org/elasticsearch/ElasticsearchException.java

@@ -80,7 +80,7 @@
 import static org.elasticsearch.cluster.metadata.IndexMetadata.INDEX_UUID_NA_VALUE;
 import static org.elasticsearch.common.xcontent.XContentParserUtils.ensureExpectedToken;
 import static org.elasticsearch.common.xcontent.XContentParserUtils.ensureFieldName;
-import static org.elasticsearch.search.crossproject.CrossProjectIndexExpressionsRewriter.NO_MATCHING_PROJECT_EXCEPTION_VERSION;
+import static org.elasticsearch.search.crossproject.IndexExpressionsRewriter.NO_MATCHING_PROJECT_EXCEPTION_VERSION;
 
 /**
  * A base class for all elasticsearch exceptions.