exec_profile_handle: allow public access to associated profile

Last time, I introduced getters for `ExecutionProfile`.
However, I forgot that in cpp-rust-driver use case, we only have
an access to `ExecutionProfileHandle`...

Since, we can convert handle to builder, I see no objections against
having the ability to convert it to well-defined execution profile.

Obviously, we need to clone an `Arc`. But only a single one.
Notice, however, that when converting to builder,
we need to clone multiple Arcs anyway (e.g. retry or load balancing policies).

scylla/src/transport/execution_profile.rs

@@ -513,6 +513,11 @@ impl ExecutionProfileHandle {
         self.0 .0.load().to_builder()
     }
 
+    /// Returns execution profile pointed by this handle.
+    pub fn to_profile(&self) -> ExecutionProfile {
+        ExecutionProfile(self.access())
+    }
+
     /// Makes the handle point to a new execution profile.
     /// All entities (queries/Session) holding this handle will reflect the change.
     pub fn map_to_another_profile(&mut self, profile: ExecutionProfile) {