Replace grape-route-helpers with our own grape-path-helpers
This gem (https://gitlab.com/gitlab-org/grape-path-helpers) makes a number of changes:
- Brings in @mdelaossa's changes in https://github.com/reprah/grape-route-helpers/pull/21
- Fixes some broken specs and code for Grape 1.0+
- Optimizes the generation of paths by bringing in @dblessing's HashWithIndifferentAccess changes in https://gitlab.com/gitlab-org/gitlab-ce/issues/45718#note_70123793
Closes #45718 (closed)