RFR: 8253179: Replace LinkedList Impl in net.http.Http2Connection

[Conor Cleary]

This patch replaces a LinkedList data structure used in the net.http.Http2Connection class with an ArrayList. This
issue relates to [JDK-8246048: Replace LinkedList with ArrayLists in
java.net](https://bugs.openjdk.java.net/browse/JDK-8246048).

Some justifications for this change are as follows:

- Sequential Access Times for ArrayLists are improved due to locality of reference (i.e ArrayList elements stored in same
  memory neighborhood)
- Get(index) operations are O(1) time complexity for ArrayLists as opposed to worst-case O(N-1) for LinkedLists
- While insertion operations can be expensive (O(N) in the worst case), these operations appear to be
  infrequent/non-existent in this case.

Additional justifications or challenges to those listed are welcome! The general idea is that ArrayLists out-perform
LinkedLists in this scenario.

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Commit messages:
 - 8253179: Replace LinkedList Impl in net.http.Http2Connection

Changes: https://git.openjdk.java.net/jdk/pull/431/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=431&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253179
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/431.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/431/head:pull/431

PR: https://git.openjdk.java.net/jdk/pull/431