Bug 30715: Terminology for the log viewer - use 'Staff interface' instead of 'Intranet'

Bug 30715: Terminology for the log viewer - use 'Staff interface' instead of 'Intranet'

The log viewer (Tools > Additional tools > Log viewer) uses
'Intranet' as:
- an option for filtering what log entries to display.
- a value in the log entries interface column, for log entries.

Koha's terminology guideline is to use 'Staff interface' instead of
'Interface' (https://wiki.koha-community.org/wiki/Terminology#I).

Test plan:
1. Perform some actions that will create log entries when using the
   staff interface. For example:
   1.1 Enable the UseRecalls system preference.
   1.2 Edit the title for a record.
   1.3 Add an item for a record.
2. Use the log viewer to view the logged changes:
   2.1 Go to Tools > Additional tools > Log viewer.
   2.2 Select Submit.
   2.3 Log entries are displayed for the changes made.
3. Note that:
   3.1 For the log viewer 'Interface' filter options, "All" is
       selected by default, and other options are Intranet, OPAC,
       SIP, Command-line, REST API, and Cron job.
   3.2 For the changes viewed in step 2, the value displayed in
       the 'Interface' column is 'Intranet'.
4. Apply the patch.
5. Refresh the page.
6. Note that:
   5.1 For the interface filter options, 'Intranet' is now changed
       to 'Staff interface'.
   5.2 In the list of log entries, the value in the interface column
       is now 'Staff interface'.
7. Sign off D:

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Emily Lamancusa <emily.lamancusa@montgomerycountymd.gov>
Signed-off-by: wainuiwitikapark <wainuiwitikapark@catalyst.net.nz>