Rework: Enum typename considering name in enumeratedValues

This pull request is a rework to #612; it only considers enumeration name
other than writer structure and reader structure. Names to those two
proxy structures are yet to be discussed.

svd2rust has a good mechanism to parse enumeratedValues into Rust enums.
However, current code would pick name of the first field the enum resides,
and use `pub type` to re-export it into other names.

SVD files provide `name` field in enumeratedValues, this commit make use of
them to name the Rust enums it generated.
After this commit, more information of SVD file is considered in output pac crate.
Users may also discover a significant drop in amount of types, which will speed up
rustdoc generation and crate compilation.

This commit is tested on deriving enum from other peripherals and
registers, and it uses old convention of format! macro to match the
1.51.0 minimum supported Rust version.

Author: luojia65

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+- Generated enum names now consider `name` field in `enumeratedValues`
 - Use constant case for structure names; internal rearrangements for
   case conversation traits
 - Add new feature `feature_group` which will generate cfg attribute for