This commit adjusts the configuration of the minimal zephyr build to use
MICROPY_CONFIG_ROM_LEVEL_MINIMUM.  That's a lot cleaner than explicitly
enabling/disabling options.

Prior to this change the minimal build for qemu_cortex_m3 had size:

    Memory region         Used Size  Region Size  %age Used
               FLASH:      114436 B       256 KB     43.65%
                 RAM:       26320 B        64 KB     40.16%

and had the following test results (running using the CI settings, ie
`-d basics float --exclude inf_nan_arith`):

    352 tests performed (7092 individual testcases)
    352 tests passed
    254 tests skipped: ...

With the changes here the qemu_cortex_m3 size is now:

    Memory region         Used Size  Region Size  %age Used
               FLASH:       99428 B       256 KB     37.93%
                 RAM:       26312 B        64 KB     40.15%

That's a good decrease of about 15k firmware size.  And the test suite
still passes with:

    342 tests performed (6776 individual testcases)
    341 tests passed
    265 tests skipped: ...

Signed-off-by: Damien George <damien@micropython.org>

This commit adjusts the configuration of the standard zephyr build to use
MICROPY_CONFIG_ROM_LEVEL_BASIC_FEATURES.  That's a lot cleaner than
explicitly enabling/disabling options, and allows boards to more easily
fine-tune the settings, eg select a different feature level.

Features that are now enabled are:
- async/await keyword support
- `filter`, `property` and `reversed` builtins
- `range` attributes
- `str.count()` method
- `array` module with `array.array` object
- `collections` module with `collections.namedtuple` object
- `struct` module with everything
- `id = const()` and constant folding in the compiler

Bulding qemu_cortex_m3, the code size was originally:

    Memory region         Used Size  Region Size  %age Used
               FLASH:      193864 B       256 KB     73.95%
                 RAM:       61992 B        64 KB     94.59%

and with this commit it is now:

    Memory region         Used Size  Region Size  %age Used
               FLASH:      200698 B       256 KB     76.56%
                 RAM:       61992 B        64 KB     94.59%

That's a mild increase of +6834 bytes flash usage for a good selection of
new features.

Signed-off-by: Damien George <damien@micropython.org>

Signed-off-by: Ned Konz <ned@metamagix.tech>

…rd files.

Signed-off-by: Ned Konz <ned@metamagix.tech>

…ython#17680.

@dpgeorge's PR micropython#17680 defines the standard Zephyr config based on MICROPY_CONFIG_ROM_LEVEL_BASIC.
This allows for simplifying the XIAO BLE board's mpconfigport-xiao.h.

Signed-off-by: Ned Konz <ned@metamagix.tech>

Signed-off-by: Ned Konz <ned@metamagix.tech>

…ectory.

Signed-off-by: Ned Konz <ned@metamagix.tech>