This is more or less a complete re-organization of the code.
* Use the actual byte size of the .bin file as the flash size,
as the algorithm for packing sections into the flash is complicated
* Match each section to a data region & find the high water mark in the
region
* Report on all the RAM regions, separately
Note that elftools is a requirement of esp-idf and so does not need to
be listed in our requirements.txt.
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