Makefile,internal/collector: Rename collector -> store

Since the removal of collector, this introduces both the concept of the
store and the resources instead of collectors that the user passes in.

The user facing logs and flags were not changed as that would be a
regression.

Makefile

@@ -42,7 +42,7 @@ doccheck: generate
 	@git diff --exit-code
 	@echo "- Checking if the documentation is in sync with the code..."
 	@grep -hoE '(kube_[^ |]+)' docs/* --exclude=README.md| sort -u > documented_metrics
-	@sed -n 's/.*# TYPE \(kube_[^ ]\+\).*/\1/p' internal/collector/*_test.go | sort -u > tested_metrics
+	@sed -n 's/.*# TYPE \(kube_[^ ]\+\).*/\1/p' internal/store/*_test.go | sort -u > tested_metrics
 	@diff -u0 tested_metrics documented_metrics || (echo "ERROR: Metrics with - are present in tests but missing in documentation, metrics with + are documented but not tested."; exit 1)
 	@echo OK
 	@rm -f tested_metrics documented_metrics