feat: add IP SSH bulk-mode support to system resource

- Add ip_ssh_bulk_mode boolean attribute to enable SSH bulk-mode
- Add ip_ssh_bulk_mode_window_size attribute (range: 131072-1073741824 bytes)
- Update CHANGELOG.md with new attributes
- Generate provider code, tests, examples, and documentation

YANG Model Reference:
- Path: /native/ip/ssh/bulk-mode
- File: Cisco-IOS-XE-ip.yang (lines 4598-4610)
- Type: Presence container with optional window-size leaf

CLI Commands Enabled:
- ip ssh bulk-mode
- ip ssh bulk-mode window-size <value>

Author: camschae