az network bastion ssh + AAD fails with "WARNING: UNPROTECTED PRIVATE KEY FILE!"

### Describe the bug

When using `az network bastion ssh --auth-type AAD` the SSL certificate is automatically added to `/tmp/aadsshcert...` but the file permissions are set such that OpenSSH 8.2 fails with

```output
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/tmp/aadsshcert23cd5o7q/id_rsa' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
```

which means the connection cannot be established.

I know the bastion command delegates this work to the ssh extension, so this is probably more of an issue for the ssh extension authors to address.

### Related command

`az network bastion ssh --auth-type AAD`

### Errors

```output
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/tmp/aadsshcert23cd5o7q/id_rsa' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
```

### Issue script & Debug output

```output
cli.azext_ssh.ssh_utils: Running ssh-keygen command ssh-keygen -f /tmp/aadsshcert23cd5o7q/id_rsa -t rsa -q -N
...
cli.azext_bastion.custom: Running ssh command /usr/bin/ssh chkittel@microsoft.com@localhost -i /tmp/aadsshcert23cd5o7q/id_rsa -o CertificateFile=/tmp/aadsshcert23cd5o7q/id_rsa.pub-aadcert.pub -p 34457 -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=Error
```

### Expected behavior

**The generated `id_rsa` file is set to permissions of `600`.**

As a bonus, I think it could even to set to `400` since this directory is transient by nature. The temp directory (`aadsshcert23cd5o7q` in this specific example above) could even be set to `700` as well for added security/intent hygiene.

### Environment Summary

```output
azure-cli 2.49.0

core 2.49.0
telemetry 1.0.8

Extensions:
bastion 0.2.4
resource-graph 2.1.0
ssh 1.1.6

Dependencies:
msal 1.20.0
azure-mgmt-resource 22.0.0
```

### Additional context

_No response_