Use lowercase for charsets #11741

Fix #11741 as per the WhatTFWG recommendations, use lower case for charset names.
Took the opportunity for some minor optimizations:
 + use the already made HttpField instance in MimeTypes.Type rather than create a new one in the HttpParser.CACHE
 + keep the MimeType.Type associated with the pre encoded Content-Type fields

jetty-ee10/jetty-ee10-servlet/src/test/java/org/eclipse/jetty/ee10/servlet/ResponseHeadersTest.java

@@ -40,6 +40,7 @@
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.equalToIgnoringCase;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.nullValue;
@@ -146,7 +147,7 @@ protected void doGet(HttpServletRequest req, HttpServletResponse response) throw
 
         // Now test for properly formatted HTTP Response Headers.
         assertThat("Response Code", response.getStatus(), is(200));
-        assertThat("Response Header Content-Type", response.get("Content-Type"), is("text/plain;charset=utf-8"));
+        assertThat("Response Header Content-Type", response.get("Content-Type"), equalToIgnoringCase("text/plain;charset=utf-8"));
 
         String expected = StringUtil.replace(actualPathInfo, "%0A", " "); // replace OBS fold with space
         expected = URLDecoder.decode(expected, StandardCharsets.UTF_8); // decode the rest

jetty-ee11/jetty-ee11-servlet/src/test/java/org/eclipse/jetty/ee11/servlet/ResponseHeadersTest.java

@@ -41,6 +41,7 @@
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.endsWith;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.equalToIgnoringCase;
 import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.not;
 import static org.hamcrest.Matchers.nullValue;
@@ -147,7 +148,7 @@ protected void doGet(HttpServletRequest req, HttpServletResponse response) throw
 
         // Now test for properly formatted HTTP Response Headers.
         assertThat("Response Code", response.getStatus(), is(200));
-        assertThat("Response Header Content-Type", response.get("Content-Type"), is("text/plain;charset=utf-8"));
+        assertThat("Response Header Content-Type", response.get("Content-Type"), equalToIgnoringCase("text/plain;charset=utf-8"));
 
         String expected = StringUtil.replace(actualPathInfo, "%0A", " "); // replace OBS fold with space
         expected = URLDecoder.decode(expected, StandardCharsets.UTF_8); // decode the rest

jetty-ee9/jetty-ee9-servlet/src/test/java/org/eclipse/jetty/ee9/servlet/ResponseHeadersTest.java

@@ -44,6 +44,7 @@
 import org.junit.jupiter.api.Test;
 
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalToIgnoringCase;
 import static org.hamcrest.Matchers.is;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -242,7 +243,7 @@ public void testMultilineResponseHeaderValue() throws Exception
 
         // Now test for properly formatted HTTP Response Headers.
         assertThat("Response Code", response.getStatus(), is(200));
-        assertThat("Response Header Content-Type", response.get("Content-Type"), is("text/plain;charset=UTF-8"));
+        assertThat("Response Header Content-Type", response.get("Content-Type"), equalToIgnoringCase("text/plain;charset=utf-8"));
 
         String expected = StringUtil.replace(actualPathInfo, "%0a", " ");  // replace OBS fold with space
         expected = StringUtil.replace(expected, "%0A", " "); // replace OBS fold with space