Fix SSH auth failures by enforcing IdentitiesOnly=yes (#4095)

## Changes
I faced this issue myself when trying the expermental ssh tunnel. since
I have couple of keys loaded into my ssh-agent

When a specific ssh key is provided via `-i` or IdentityFile option,the
SSH client still attempt to auth using all keys loaded in the ssh-agent
first. If too many keys are loaded, this causes the server to reject the
connection with "Too many authentication failures" before the correct
key is attempted.

## Why
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might be missing.
For example, were there any decisions behind the change that are not
reflected in the code itself? -->

## Tests
manually tested the change

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Author: hamza-db

experimental/ssh/internal/client/client.go

@@ -252,6 +252,7 @@ func spawnSSHClient(ctx context.Context, userName, privateKeyPath string, server
 	sshArgs := []string{
 		"-l", userName,
 		"-i", privateKeyPath,
+		"-o", "IdentitiesOnly=yes",
 		"-o", "StrictHostKeyChecking=accept-new",
 		"-o", "ConnectTimeout=360",
 		"-o", "ProxyCommand=" + proxyCommand,

experimental/ssh/internal/setup/setup.go

@@ -96,6 +96,7 @@ Host %s
     User root
     ConnectTimeout 360
     StrictHostKeyChecking accept-new
+    IdentitiesOnly yes
     IdentityFile %q
     ProxyCommand %s
 `, opts.HostName, identityFilePath, proxyCommand)