ref(normalization): Reduce processor module visibility (#2729)

The are a lot of tests requiring `NormalizeProcessor` in
`transactions/processor.rs`, forcing higher visibility than necessary on
`normalize/processor.rs`. This PR moves required tests from one module
to another, thus reducing the required module visibility. As we continue
to refactor the processors, we'll find a better home for functions and
tests.

Author: iker-barriocanal

relay-event-normalization/src/normalize/mod.rs

@@ -30,14 +30,14 @@ use crate::{
 
 pub mod breakdowns;
 pub mod nel;
-pub(crate) mod processor;
 pub mod span;
 pub mod user_agent;
 pub mod utils;
 
 mod contexts;
 mod logentry;
 mod mechanism;
+mod processor;
 mod request;
 mod stacktrace;