deduplicate RegisterBlockExt impls code

Author: burrbull

CHANGELOG-rust.md

@@ -7,6 +7,7 @@ This changelog tracks the Rust `svdtools` project. See
 
 * Allow to modify registers in `_cluster:`
 * Add addressOffset check in `collect_in_cluster`
+* Refactor `RegisterBlockExt`, use `BlockPath` for better errors
 
 ## [v0.3.11] 2024-03-06