Use new terminal find API

Fixes #30633

This brings in:

- UIEvent.detail usage
- Search addon refactor

Fixes #20505

This was to be used by tasks as an extenion which ended up
not happening.

Investigating #30449, it seems that typescript refactoring can take a long time to compute in some projects. Disabling these in insiders. We'll disable them in 1.14 is this is found to help

Fix Microsoft/monaco-editor#505. On IE11, we need to set width explicitly, otherwise Flexbox width inheritance doesn't always work.