Bug 4577 Allow specification of a distinct schema cache directory per netconf device

Bug 4577 Allow specification of a distinct schema cache directory per netconf device

First iteration done here https://git.opendaylight.org/gerrit/#/c/30163 introduce a BUG:
sideloaded schemas, manually added in cache/schema, and specified in the netconf connector,
where not being taking in account in the specified cache folder.

This path add the capability to register the sideloaded schema in the new FilesystemSchemaSourceCache

Change-Id: I6a5a6b23fc56bcc507734a99e48de88597b7ae2a
Signed-off-by: adetalhouet <adetalhouet@inocybe.com>