Filter doesn't show an option for "os"

### Environment

SaaS (https://sentry.io/)

### Steps to Reproduce

1. Go to issues
2. Click into the Search field
3. write "os"

### Expected Result

There should be "os" filter (This filter actually works if you go to an Issue -> Tags -> Search values with this tag).
Also, there should probably be an "os.name" filter, considering we automatically create this tag based on the "os" context.

### Actual Result

### Product Area

Issues

### Link

_No response_

### DSN

_No response_

### Version

_No response_

The issue points to the Issues search field and the existing tag-value search path, but names no files or tests. Start by tracing how filter options are populated for "os", then verify that "os" and "os.name" are offered while the existing tag filtering still works.

Written by the indexing model from the issue text.