Heap unification

[JF002]

This PR unifies the 3 memory heaps used in InfiniTime (stdlib, LVGL and FreeRTOS) into a single memory space managed by FreeRTOS.

The goals are

• Reduce the memory overhead caused by those 3 heaps
• Provide an easy way to monitor the memory usage at runtime
• Provide a better overview of the memory allocation.

According to the memory analysis I've previously done, dynamic memory allocations (which consume heap memory) are done in multiple parts of the code:

• LVGL
• use of new() and delete() (std::string, std::unique_ptr, apps loading in InfiniTime)
• LittleFS
• NimBLE

LVGL support custom memory manager, so I simply edited the configuration to point the alloc/free functions to FreeRTOS memory manager. For other parts of the code that use malloc(), delete(), new(), free(), I defined custom implementations of malloc(), free(), realloc() so that they'll be linked in the code in place of the ones from stdlib. This ensures that the heap from stdlib is not used anymore.

In the end, here's a rough overview of the memory allocation:

• Total memory available : 65536B
• Memory allocated : 63728B + 1024B (stack) = 64752B
• FreeRTOS heap : 40960B

This leaves 784B unallocated at build time.

I used this branch for multiple days and the minimum memory available in the FreeRTOS heap was around 6KB. Which means that we still have ~6KB of RAM available for static allocation (we'll need a bit of this for the new HR implementation) or for dynamic allocation (for new apps, fonts,...).

[github-actions[bot]]

Build size and comparison to main:	Section	Size	Difference
text	406104B	-352B
data	940B	0B
bss	62772B	9212B

[kieranc]

Initital testing looks good, I can switch from PTS to G7710 to Infineat without corrupted fonts.