Make miter limit and arc tolerance configurable for polypath offsetting

[Xrayez]

Supersedes #29758 (makes API not consistent due to binding limit without including core/method_bind_ext.gen.inc which would result in engine binary size bloat, AFAIK).

Closes #29886.

The first commit breaks compat by combining PolyJoinType and PolyEndType into a single PolyConnection enum. The second commit exposes both miter and arc parameters which was impossible to do due to binding limit of 5 parameters. I can squash these together if the changes are acceptable.

Example

# Produces a thin corridor with round corner passages and dead-ends.
var polyline = [Vector2(0, 0), Vector2(100, 0), Vector2(100, 100), Vector2(0, 100)]
var polygons = Geometry.offset_polyline_2d(polyline, 20.0, Geometry.JOIN_ROUND | Geometry.END_BUTT)

var polygons = Geometry.offset_polyline_2d(polyline, 20.0, Geometry.JOIN_MITER | Geometry.END_ROUND)

Test project

geometry-clipper-test.zip

[Xrayez]

Closing this for now due to the same reasons as in #35929 (comment).

This probably has to be approved first godotengine/godot-proposals#913.