DefaultEndPoint.equals blocks on DNS and is inconsistent with hashCode for unresolved vs resolved addresses

[nikagra]

DefaultEndPoint.equals resolves the unresolved side before comparing:

if (thisAddress.isUnresolved() && !thatAddress.isUnresolved()) {
  thisAddress = new InetSocketAddress(thisAddress.getHostName(), thisAddress.getPort());
} // ...

Three problems with that branch:

1. It blocks. new InetSocketAddress(String, int) performs a DNS lookup inline on the calling
   thread. equals() is called from metadata refresh paths and from event handling on the admin
   event loop, so a slow or unreachable resolver stalls a driver thread inside what reads like a
   field comparison.
2. The answer is arbitrary. That constructor keeps only the first address the name maps to,
   so for a multi-record name the result is "equal iff this node happens to be the one the resolver
   listed first" — it flips as DNS ordering changes.
3. It is inconsistent with hashCode(), which is address.hashCode() and ignores resolution
   entirely. So a hostname and one of its IPs can be equals while hashing differently, and
   hash-based collections never treat them as the same entry — including the contact-point
   Set<EndPoint> (SessionBuilder.programmaticContactPoints, ContactPoints.merge), where a
   mixed pair for the same host is silently kept twice.

The lenient comparison therefore only ever takes effect on linear scans, and where it does take
effect it is neither cheap nor deterministic.

Proposal

Compare address as-is and drop the resolving branch, making equals/hashCode consistent for
the first time. The only remaining consumer of the lenient behaviour is the public
Metadata.findNode(EndPoint), so this needs an upgrade-guide entry: a caller holding an unresolved
hostname endpoint would no longer find a node registered under its resolved IP (which today it
finds only when that IP is the name's first record anyway).

Signal to watch first

DRIVER-201 (#890) removed every driver-internal mixed comparison and added a one-shot WARN on
this branch. If that warning does not show up in the field, nothing outside findNode relies on
it and the branch can go.