Integrate meta-guf-distro/shared-conf-splitstring
sharedconf: gf-functions: Add function to split strings, cleanup
The split function allows to split strings by a given separator, optionally search in the split results, and combine the splited elements to a result string.
Use the splitfunction where it replaces the previous implementation directly.
Rename some local function variables with the function name as prefix. There are no real 'local' varaibles in posix shell, so this is a workarround which reduce the risk of name clashing.