Uniform header inclusion

[AntoinePrv]

No description provided.

[serge-sans-paille]

That's cool, but you also need tow rite some rule to ensure we don't regress on those, otherwise we're going to repeateadly have this.

I think I prefer having standard header include last, as a way to detect some missing includes hidden by transitive inclusion. This can be enforced by the following clang-format option:

IncludeBlocks: Regroup
IncludeCategories:
  - Regex:           '"\.\.?/.*"'
    Priority:        2
    SortPriority:    2
  - Regex:           '<.*'
    Priority:        3