Update to latest rust-layers

We now need to pass through the content age of the LayerBuffer when
creating it.
Mark all layers as having changed content during pinch zoom

This ensures that layers know that they need to re-issue buffer
requests immediately instead of waiting until another content change
happens.

Fixes #2988.
Merge pull request #3097 from mrobinson/pinch-zoom-delay

Update rust layers and fix delay in pinch zoom
initial cookies with domain validations and improper storage
finished cookie attrs parsing

now onto storage model (rfc 6265#section-5.3)
cookies struct finished
added cookies tests
cookies wip