In the future, it is planned to extend the URI structure to allow its
passing with different options and in different formats (see next commit
`uri: implement ability to parse URI query paramters` for example). For
these purposes, it is planned to use functions that modify the source
string, for example `strtok_r`, so we need to rework the URI structure
to create copies of the string for each of the URI components.

Part of #5928