Get the fabric index

[todo]

connectedhomeip/src/protocols/secure_channel/CASESession.cpp

Lines 138 to 148 in 7304eaa

	// TODO: Get the fabric index
	cachableSession.mLocalFabricIndex = 0;
	cachableSession.mSessionSetupTimeStamp = LittleEndian::HostSwap64(mSessionSetupTimeStamp);
	memcpy(cachableSession.mResumptionId, mResumptionId, sizeof(mResumptionId));
	memcpy(cachableSession.mSharedSecret, mSharedSecret, mSharedSecret.Length());
	return CHIP_NO_ERROR;
	}
	CHIP_ERROR CASESession::FromCachable(const CASESessionCachable & cachableSession)

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This issue was generated by todo based on a TODO comment in 7304eaa when #11937 was merged. cc @nivi-apple.