esp32/machine_rtc: ESP32 machine.RTC().usermem() returning a bytearray.

[karfas]

Returns a bytearray referencing the user memory area of an ESP32 RTC.

This somewhat overlaps with RTC().memory(), but allows to address the entire user memory (e.g. using the uctypes functions) without knowing the exact address of the user memory area.

I would have preferred to create an attribute/property (e.g. RTC().usermem) for this, but that is way too complicated in the C API.

Previous:

mem = uctypes.bytearray_at(0x50000200, 2048) # user needs to know address + size
uctypes.addressof(RTC().memory())                     # address completely unrelated to RTC memory

Afterwards:

mem = machine.RTC().usermem()     # no need to consult source and linker map
addr = uctypes.addressof(mem)         # REAL address of RTC memory

[karfas]

Added documentation. This hijacks PR #5199, where machine.RTC.memory() is documented.

[karfas]

@jimmo, @dpgeorge: This is now two years old.
Maybe you find time for a review ?

[projectgus]

This is an automated heads-up that we've just merged a Pull Request
that removes the STATIC macro from MicroPython's C API.

See #13763

A search suggests this PR might apply the STATIC macro to some C code. If it
does, then next time you rebase the PR (or merge from master) then you should
please replace all the STATIC keywords with static.

Although this is an automated message, feel free to @-reply to me directly if
you have any questions about this.