ContextHubEventLogger: Add reliable message error logging

This CL adds logging for reliable messages sent to nanoapps.
The error code will now be tracked.

Bug: 333567700
Flag: EXEMPT bugfix
Test: atest ContextHubEventLoggerTest
Test: Build, flash, run the reliable message test
      -> adb shell dumpsys contexthub shows error codes

Change-Id: I80e05dac90d77b3dc2bc98147cb3e82aeede0725