Update dashboards to drive issues and merge requests without subtypes to near zero

These dashboard changes will allow us to track issues and merge requests without a subtype label over time so we can drive them to near zero.

Tasks for subtype undefined issues

In dashboard https://app.periscopedata.com/app/gitlab/1042933/Issue-Types-by-Milestone

• Add a graph similar to the "issues by type graph" by milestone that shows the number of issues that have a type label and subtype label (line 1) and ones that have a type label and do not have a subtype label (line 2). This will allow us to see the trends over time to ensure we are getting to near zero.
• In this same dashboard, add a table similar to "project search for undefined issues" but that will show issues that have a type label but not have a subtype label. This will allow us to quickly find the issues and add a label.

Tasks for subtype undefined merge requests

• Copy the "MR Types" graph from https://app.periscopedata.com/app/gitlab/976854/Merge-Request-Types-Detail and make it by milestone rather than by month. This will allow us to track undefined merge requests in the same way we do for undefined issues.
• Create a version of the "MR Types" graph that plots the number of merge requests that have a type label and subtype label (line 1) and ones that have a type label and do not have a subtype label (line 2). This will allow us to see the trends over time to ensure we are getting to near zero for merge requests.
• Add a table similar to "project search for undefined issues" but that will show merge requests that do not have a type label. This will allow us to quickly find the merge requests and add a label.
• Add a table similar to "project search for undefined issues" but that will show merge that have a type label but do not have a subtype label. This will allow us to quickly find the merge requests and add a type label.