Load containers to external memory, when available

[kr-t]

Description

This PR mostly includes support for external memory on U585, but also creates a platform for easy support for other platforms as well.

• Added support for external flash: containers still stored on LFS, which is now stored on external memory. External memory can be cleaned via user_storage format shell command or STM32_Programmer_CLI -c port=swd -el "/usr/local/STMicroelectronics/STM32Cube/STM32CubeProgrammer/bin/ExternalLoader/MX25LM51245G_STM32U585I-IOT02A.stldr" -e all -s host command or via other tools (like CubeProgrammer)
• Added support to load containers into PSRAM
• Input binaries are now stored in flash (via const keyword)
• Added a sample for big binary (~1 MB) to showcase the use case for external memory support (https://github.com/project-ocre/ocre-sdk/tree/main/generic/big-sample)

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

All containers are started and work as expected below:

./build.sh -t z -r
./build.sh -t z -r -f ~/demos/ocre-sdk/generic/blinky/build/blinky.wasm 

./build.sh -t z -r -b uw 
./build.sh -t z -r -b uw -f ~/demos/ocre-sdk/generic/webserver/build/webserver.wasm 
./build.sh -t z -r -b uw -f ~/demos/ocre-sdk/generic/big-sample/build/big-sample.wasm 
./build.sh -t l -r -f ~/demos/ocre-sdk/generic/blinky-board-generic/build/blinky-board-generic.wasm 

 ./build.sh -t l -r -f ~/demos/ocre-sdk/generic/messaging/publisher/build/publisher.wasm ~/demos/ocre-sdk/generic/messaging/subscriber/build/subscriber.wasm
./build.sh -t l -r -f ~/demos/ocre-sdk/generic/webserver/build/webserver.wasm 
./build.sh -t l -r -f ~/demos/ocre-sdk/generic/blinky/build/blinky.wasm 

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes

[kr-t]

This will also
close #86