perf: optimized request headers (#1335)

* Optimizes header registration.

* Adds malformed cookie tests.

* Sets key to NULL (releasing them is unnecessary)

* Adjusts test.

* Sanitizes null bytes anyways.

* Sorts headers.

* trigger

* clang-format

* More clang-format.

* Updates headers and tests.

* Adds header test.

* Adds more headers.

* Updates headers again.

* ?Removes comments.

* ?Reformats headers

* ?Reformats headers

* renames header files.

* ?Renames test.

* ?Fixes assertion.

* test

* test

* test

* Moves headers test to main package.

* Properly capitalizes headers.

* Allows and tests multiple cookie headers.

* Fixes comment.

* Adds otter back in.

* Verifies correct capitalization.

* Resets package version.

* Removes debug log.

* Makes persistent strings also interned and saves them once on the main thread.

---------

Co-authored-by: Alliballibaba <alliballibaba@gmail.com>

testdata/server-all-vars-ordered.php

@@ -4,6 +4,8 @@ echo "<pre>\n";
 foreach ([
              'CONTENT_LENGTH',
              'HTTP_CONTENT_LENGTH',
+             'CONTENT_TYPE',
+             'HTTP_CONTENT_TYPE',
              'HTTP_SPECIAL_CHARS',
              'DOCUMENT_ROOT',
              'DOCUMENT_URI',
@@ -11,10 +13,8 @@ foreach ([
              'HTTP_HOST',
              'HTTPS',
              'PATH_INFO',
-             'CONTENT_TYPE',
              'DOCUMENT_ROOT',
              'REMOTE_ADDR',
-             'CONTENT_LENGTH',
              'PHP_SELF',
              'REMOTE_HOST',
              'REQUEST_SCHEME',
@@ -27,7 +27,6 @@ foreach ([
              'SSL_PROTOCOL',
              'AUTH_TYPE',
              'REMOTE_IDENT',
-             'CONTENT_TYPE',
              'PATH_TRANSLATED',
              'QUERY_STRING',
              'REMOTE_USER',