refactor(shell): Improve shell command naming and output formatting

- Renamed shell commands in  and  to be shorter
  and remove underscores (e.g.,  to ).
- Consolidated get functions into a single show command for both valve
  and Modbus settings (e.g., , ).
- Adjusted output formatting for show commands to be right-aligned and
  remove horizontal lines for better readability.
- Fixed missing getter function implementations in  and their
  declarations in .
- Ensured  is correctly selected in
  to make valve shell commands available.

software/apps/slave_node/prj.conf

@@ -5,6 +5,9 @@ CONFIG_LOG=y
 # Enable Shell
 CONFIG_SHELL=y
 CONFIG_REBOOT=y
+CONFIG_SHELL_MODBUS=y
+CONFIG_SHELL_VALVE=y
+CONFIG_SHELL_SYSTEM=y
 
 # Enable Settings Subsystem
 CONFIG_SETTINGS=y