Improve linkrewriting to be able to NEST hst mounts that point to content nodes that are descendant/ancestor from each other AND to have fallback linkrewriting if some channel cannot create a link for a document

If you have a configuration like this:

global (mount)
sub1 (mount)
sub2 (mount)

content
global
sub1
sub2

and you have:

mount 'global' --> /content/global
mount 'global/sub1' --> /content/global/sub1
mount 'global/sub2' --> /content/global/sub2

This currently does not work for at least 3 things (assuming 'global' is only for search)

1) For the preview from the cms (will try to resolve link in 'global')
2) For internal document links between documents below sub1 to docs
in sub2 and vice versa
3) For global search

I'd like to provide rather a real fix, that covers all the 3 issues in one go

I'd like to change the current linkrewriting behaviour as follows:

1) When multiple Mounts have a 'root' content path that are suited to
linkrewrite a document, we pick the Mount that has the deepest 'root'
path and try this mount first
2) When multiple Mounts have a 'root' content path that is suited to
linkrewrite a document, and we tried a Mount that resulted in a
'pagenotfound' link, we try another suited Mount. If none of the
Mounts can create a link for the document, we return the first
notfound link

If I modify linkrewriting like above we:

1) have support for nested mounts that have overlapping content's (thus global mount overlaps content of sub1 and sub2)
2) Also have the use case covered where for example two channels (mobile and website) share the same content root, but some docs are
not displayable in mobile: then, a link to 'website' can be created