[Process] Add ability to force unescaping + tweaks (code & test)

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | Not sure if we want to document this ? If yes, I'll update if accepted.

Rationale:
`'ogr2ogr' '-f GeoJSON'` would not work
`'ogr2ogr' -f GeoJSON` would work

The first commit has the interesting updates, other commits are tweaks only. Everything should be squashed before the merge.