Remove sparql client dependency v2

[nvdk]

This is a rewrite of the work done in #69 to be compatible on the latest work on master.

Thanks to dropping the old and unmaintained sparql-client dependency we have a template with fewer dependencies and as such fewer possible conflicts for services. It also drops all related security warnings from npm audit.

a few notes for the reviewer:

• newSparqlClient is removed from the public API. Even though it wasn't documented in the README, it was exported and as such this could be considered a breaking change. A brief search indicates it wasn't used anywhere so this shouldn't be a major issue though.
• I've dropped the digest-fetch dependency used in the original PR and replaced it with regular fetch as this is not a good match with the template's goal. Supporting digest authentication to a sparql endpoint is better suited in a separate library.
• this is an AI assisted PR and while care was taken to avoid unnecessary rewrites of heredocs and unchanged code, some might have slipped through. If you flag them I'll happily correct them

Update:
after discussion these were removed from the PR:

• configurable retry logic from the original mu-auth-sudo code was kept, with the improvements added by @Rahien
• the option to specify the endpoint (and overwrite the default) in query and update was kept

I'll create PRs for these when this is merged.