2D Physics Collision is 'Squishy'

[DevinPentecost]

Godot version:
3.1.2.stable.official

OS/device including version:
Windows 10

Issue description:
When two a RigidBody2D collides with a StaticBody2D, they 'squish' into each other and then the RigidBody2D slowly returns to the edge of the collision over a few frames. This makes the collision not feel quite so 'rigid' but instead like the StaticBody2D is squishy and allows other bodies to enter it temporarily. I have not checked to see if this behavior presents in 3D Nodes as well.

Steps to reproduce:
Create a 2D scene with a RigidBody2D and a StaticBody2D. Have the RigidBody2D collide into the other body with some velocity. You'll observe the RigidBody2D enter the StaticBody2D.

Minimal reproduction project:
Zipped Project, open at run the scene.
Bouncy.zip

[gururise]

If you enable continuous collision detection (CCD), then the bodies should not overlap; however, CCD for 2D is currently not working, see issue #9071

[ZingBlue]

This almost breaks my entire game at times. I have no idea how to fix it either.

[Exxion]

I believe setting the custom solver bias of any collision shapes involved to 1 should fix this, though given that it doesn't default to that, doing so probably causes other problems elsewhere. At a guess, it probably causes instability with collisions involving multiple bodies.

EDIT: I tested it. It does cause some instability, but it's not that bad.
There should probably be a project setting for the default bias instead of it being hardcoded to 0.3.