[router] Refactored several allocation-heavy paths in Alpini (#827)

This includes removing Optionals and some stream functions.

Also removed some unused headers from error responses.

Deleted a bunch of unused code and its associated tests.

internal/alpini/common/alpini-common-base/src/main/java/com/linkedin/alpini/base/misc/Headers.java

@@ -4,7 +4,6 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 
 
 /**
@@ -51,8 +50,6 @@ default Headers set(Iterable<Map.Entry<String, String>> entries) {
 
   Iterator<Map.Entry<CharSequence, CharSequence>> iteratorCharSequence();
 
-  <T> Optional<T> unwrap(Class<T> type);
-
   Headers EMPTY_HEADERS = new Headers() {
     @Override
     public boolean isEmpty() {
@@ -99,11 +96,6 @@ public Iterator<Map.Entry<CharSequence, CharSequence>> iteratorCharSequence() {
       return Collections.emptyIterator();
     }
 
-    @Override
-    public <T> Optional<T> unwrap(Class<T> type) {
-      return Optional.empty();
-    }
-
     @Override
     public Iterator<Map.Entry<String, String>> iterator() {
       return Collections.emptyIterator();

internal/alpini/router/alpini-router-api/src/main/java/com/linkedin/alpini/router/api/MetricNames.java → internal/alpini/common/alpini-common-base/src/main/java/com/linkedin/alpini/base/misc/MetricNames.java

@@ -1,4 +1,4 @@
-package com.linkedin.alpini.router.api;
+package com.linkedin.alpini.base.misc;
 
 /**
  * @author Antony T Curtis {@literal <[email protected]>}