Enable Pico2 support for ExecuTorch

[psiddh]

🚀 The feature, motivation and pitch

• Add a script that cross compiles executorch for baremetal os
• Create a python script that converts a given model to hex array and bakes it into the source code . The auto generated code then gets built as a binary / firmware that could be flashed on pico2 board
• Add README instructions with the ability to test with different models

Alternatives

#12518 (In review)

Additional context

No response

RFC (Optional)

No response