Because address space is mapped in 64KB pages, it was possible for unauthenticated data after the
app .bin to become mapped into the flash cache address space.
This problem is solved by 2 changes:
* "esptool elf2image --secure-pad" will pad the image so that the signature block ends close to the
64KB boundary. Due to alignment constraints it will be 12 bytes too short after signing (but
with flash encryption, these 12 bytes are still encrypted as part of the last block and can't be
arbitrarily changed).
* By default, secure boot now requires all app partitions to be a multiple of 64KB in size.
Allows you to move the partition table, it gives more space for the bootloader.
Added a new utility - parttool.py. This utility can search for the offset and/or size of the partitions by name and type/subtype. Use for getting APP_OFFSET and PHY_DATA_OFFSET.
The linker(esp32.bootloader.ld) made changes that allow you to write a custom bootloader code more.
TW14125
For config-only components, component.mk should now contain "COMPONENT_CONFIG_ONLY := 1"
Also refactored some of the generation of linker paths, library list. This required cleaning up the way the bootloader
project works, it's now mostly independent from the parent.
* App access functions are all flash encryption-aware
* Documentation for flash encryption
* Partition read/write is flash aware
* New encrypted write function
