added triggers to check for and handle code conflicts in custom xmls (p…

…roject-chip#1402)

- Added triggers to check for mfg code and code conflicts in custom xml.
- When a session package (that is a manufacturer specific custom xml) is inserted or re-enabled these triggers check for the following:
	*If any other XMLs linked to the same session have cluster code conflicts
	*If any other XMLs extend the same cluster and have attribute or command code conflicts
- and adds the relevant session notifications
- Also added triggers to delete all code conflict session notifications related to a session package when that session package is deleted/disabled
- Updated relevant tests to check for these session notifications

ZAPP-1467