The ADP536X integrated circuit interfaces with two distinct drivers:
the Zephyr regulator driver, responsible for power regulation aspects
of the ADP536X, and the sdk-nrf ADP536X driver, which manages other
functionalities. Both drivers are now reserved exclusively for
inclusion within the application image.

Introduced a new kconfig symbol IS_BOOTLOADER_IMG, to simplify checking
for both MCUboot and secure bootloaders.

In addition, changed how the driver is automatically enabled. Now it is
enabled if the devicetree has an "adi,adp5360" compatible node enabled.

CIA-604

Signed-off-by: Gregers Gram Rygg <gregers.gram.rygg@nordicsemi.no>

Move static partition logic for thingy:91 out to separate Kconfig
options:

CONFIG_THINGY91_STATIC_PARTITIONS_FACTORY for the original factory
partition layout. This is the default.

CONFIG_THINGY91_STATIC_PARTITIONS_SECURE_BOOT for a partition layout
similar to the factory layout, but it has the immutable bootloader and
partitions for uptadable bootloader. This is still experimental.

CONFIG_THINGY91_STATIC_PARTITIONS_LWM2M_CARRIER for a partition layout
that has the partitions needed to use the lwm2m carrier library.

CIA-604

Signed-off-by: Gregers Gram Rygg <gregers.gram.rygg@nordicsemi.no>

Allow using none of the pre-defined static partition layouts for
thingy:91. This allows the application to use a dynamic layout or
define a custom static partition layout for the application.

Signed-off-by: Gregers Gram Rygg <gregers.gram.rygg@nordicsemi.no>