Dashboard Filter by Metrics datatype

### Problem Statement

We have recently started using Sentry metrics to track mobile app events (with great success). While metrics using metrics in queries we are able to filter by metric attributes (e.g. filtering by a userID). Sometimes I have multiple metrics that I want to apply the same filter to, which is possible in queries... but requires that I add the filter to each query

In dashboards there is the ability to add global filters... but while metric graphs can be added to dashboards, there is no ability to select metrics as a datatype when adding a filter.

### Solution Brainstorm

Add the ability to filter by sentry metric attributes to dashboards :)

### Product Area

Unknown

No files or tests are identified. Start by locating dashboard global-filter handling and how metric graphs represent their datatype, then compare that with metric-attribute filtering in queries. Done means a dashboard global filter can target metric attributes and apply consistently to multiple metric graphs, with coverage for the behavior.

Written by the indexing model from the issue text.