Reimplement HTTP::URI with native component storage

Replace Addressable::URI delegation with direct instance variables for
all URI components (scheme, user, password, host, port, path, query,
fragment). ASCII URIs are now parsed with Ruby's stdlib URI module;
Addressable is only used as a fallback for non-ASCII (IRI) strings and
for IDNA host normalization.

Author: sferik

.mutant.yml

@@ -27,3 +27,5 @@ matcher:
     - HTTP::Redirector*
     - HTTP::Features::RaiseError*
     - HTTP::Base64*
+  ignore:
+    - HTTP::URI.parse_with_addressable

CHANGELOG.md

@@ -18,6 +18,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   `Response.new`, `Redirector.new`, `Retriable::Performer.new`,
   `Retriable::DelayCalculator.new`, and `Timeout::Null.new` (and subclasses).
   `HTTP::URI.new` also no longer accepts `Addressable::URI` objects.
+- Reimplement `HTTP::URI` with native component storage instead of delegating
+  to `Addressable::URI`. ASCII URIs are now parsed with Ruby's stdlib `URI`,
+  with Addressable used only as a fallback for non-ASCII (IRI) strings. This
+  removes most of the runtime dependency on the `addressable` gem while
+  preserving full URI functionality.
 - **BREAKING** Extract request building into `HTTP::Request::Builder`. The
   `build_request` method has been removed from `Client`, `Session`, and the
   top-level `HTTP` module. Use `HTTP::Request::Builder.new(options).build(verb, uri)`