Fix submenu layout is not copied on menu cells

[joeljfischer]

Fixes #2048

Risk

This PR makes no API changes.

Testing Plan

• I have verified that I have not introduced new warnings in this PR (or explain why below)
• I have run the unit tests with this PR
• I have tested this PR against Core and verified behavior (if applicable, if not applicable, explain why below).

Unit Tests

Unit tests for copying SDLMenuCell are added

Core Tests

Created a cell with a submenu with the submenu layout as TILES

Core version / branch / commit hash / module tested against: Manticore (Core v7.1.1)
HMI name / version / branch / commit hash / module tested against: Manticore (Generic HMI

Summary

This PR fixes copying a menu cell does not copy the submenu layout

Changelog

Bug Fixes

• Fixed submenu cells not using the submenu layout

Tasks Remaining:

n/a

CLA

• I have signed the CLA