Fix hostkey

[nindanaoto]

Fix connectbot/connectbot#2023.
The crash was introduced by the host key rotation feature added in sshlib 2.2.33 (commit 19b6826).

Root Cause

After authentication, OpenSSH servers (including ESXi 6.7's OpenSSH 8.6) send a hostkeys-00@openssh.com global request advertising the server's host keys.
The new processHostkeysAdvertisement code compares the algorithm names from the advertised key blobs against the algorithms stored by ConnectBot.

The problem is an RSA algorithm name mismatch:

• Key blobs always identify as ssh-rsa (the key format)
• ConnectBot stores the negotiated signature algorithm, e.g. rsa-sha2-512

These represent the same RSA key, but the code treats them as different. It concludes rsa-sha2-512 is "no longer advertised" and calls
removeServerHostKey(hostname, port, "rsa-sha2-512", null) — passing null for the host key bytes.

ConnectBot's Kotlin override declares hostKey: ByteArray (non-nullable), so Kotlin's intrinsic null-check throws a NullPointerException. This NPE
propagates uncaught through handleMessage → receiveLoop → the SSH receiver thread (which only catches IOException), killing the thread and crashing the
app.

Fix

1. Normalize RSA algorithm names — rsa-sha2-256 and rsa-sha2-512 are mapped to ssh-rsa for key identity comparison, preventing the false mismatch
2. Catch Exception (not just IOException) around processHostkeysAdvertisement so verifier callback failures can't kill the receiver thread
3. Fix global request counter — check for pending hostkeys-prove response before incrementing globalSuccessCounter, preventing interference with other
   global requests
4. Fix protocol reply — send REQUEST_SUCCESS (not REQUEST_FAILURE) for hostkeys-00@openssh.com requests we handle