GITHUB: #342

Add support for nullable fabric scoped event item support

Fix default value handling for external string attributes.

We were incorrectly outputting a default value in endpoint_config.h
for external string attributes, as long as there was a nonempty
default value set in the ZAP UI.  The fix is to make sure we don't do
that, because external attributes don't have default values.

Some SDK implementations want to force some specific storage policy
for attributes depending on implementation decisions.  Add some
mechanisms for doing that:

* Add a way to force all lists to have an "attributeAccessInterface"
  storage policy.
* Add a way to provide a map of attributes that have an
  "attributeAccessInterface" storage policy.

For now this policy is mapped to "External" storage for endpoint
attributes, but later on I want to add another value to that enum and
use it instead of "External", because there are some optimizations we
can do for "attributeAccessInterface" that we can't do for things that
are just "External".

Silabs

Silabs

Add logic that will upgrade zap file to correctly peg the reporting policy to mandatory or prohibited.

Matter field ids start at 0, not 1, but the defaulting was defaulting
to starting at 1.

The new setup defaults the first field to 0, and every following field
to 1 more than the previous one (which might have an explicitly
specified field id).

BUG: MCUDT-27166

BUG: MCUDT-27166

BUG: MCUDT-27166

Include the fieldIdentifier for command arguments.

Fix endpoint_config handling of manufacturer-specific things.

Matter uses 32-bit ids, not 16-bit ones, with the high 16 bits
representing the manufacturer id.

Silabs