Splits models into its own file

GitLens uses legacy project routes for GitLab:

- `${projectURL}/branches`
- `${projectURL}/tree/${branch}`
- `${projectURL}/commit/${sha}`
- `${projectURL}/compare/${base}${notation}${compare}`
- `${projectURL}/blob/${ref}/${fileName}`

These routes are all deprecated and scheduled for removal. See these references:

- https://docs.gitlab.com/ee/development/routing.html#project-routes
- https://gitlab.com/gitlab-org/gitlab/-/issues/118849
- https://gitlab.com/gitlab-org/gitlab/-/issues/28848

This change replaces them with the following scoped routes:

- `${projectURL}/-/branches`
- `${projectURL}/-/tree/${branch}`
- `${projectURL}/-/commit/${sha}`
- `${projectURL}/-/compare/${base}${notation}${compare}`
- `${projectURL}/-/blob/${ref}/${fileName}`

See also: https://github.com/microsoft/vscode/issues/85930

Only get stats if isDirectory is null

Increases the width of the heatmap gutter glyph
Moves gutter glyphs closer to the code

Adds line fading option to heatmap annotation