[group] Add salt to group key KDF

[turon]

Problem

If the same EpochKey is installed on two fabrics, there will be collisions with the messages.

Proposed Solution

Add a diversifier to the KDF salt for operational group key generation as being defined in:
https://github.com/CHIP-Specifications/connectedhomeip-spec/issues/4910 (issue)
https://github.com/CHIP-Specifications/connectedhomeip-spec/pull/4911 (PR)

This will make it extremely unlikely that the operational group key is the same on two fabrics even when the same epoch key input is used. Current proposal of passing CompressedFabricId as salt has 2^-64 chance of collisions. If folks want to lobby for 2^-128 chance of collisions (max key size output), we could pass RootPuclicKey || FabricID instead.

[andy31415]

V1.0 since we need to match spec.