Remove kurbo and peniko dependencies

[nicoburns]

We should probably wait until we've backported linebender_resource_handle to peniko 0.4 to land this. Then the font/blob conversion code can disappear.

We may want to name parley::Rect something more specific like parley::SelectionArea

Depends on:

• Fix clippy::obfuscated_if_else lints #415

[DJMcNab]

This is a good way to achieve the goal, and I agree with the goal. I've got some thoughts about making sure that we make clear to our users and tooling what the purpose of this new type is.

[DJMcNab]

What do you think about making this non_exhaustive (and removing pub fn new/Default), to gently discourage more general use. Obviously if people can get a single Rect, since it's Copy, they can easily make new ones, but it should be sufficient roadblocks to prevent people doing that.

I'd also consider renaming to something like OutputRect or similar. In particular, I never want Rust Analyzer to suggest this type when I am looking to import Rect.
Basically strongly saying to applications that they should standardise on a rectangle type, and it shouldn't be this one.

That would make this PR much easier for me to approve, as it makes this API much clearer.
But I'd also suggest that we can talk about this in office hours.

[nicoburns]

I guess so. I don't really care if anybody uses it, but I do agree that it would be good to remove it from autocomplete for Rect. How about a rename to BoundingBox (with an eye on using BoundingBox from the font-types crate once font-types hits 1.0.

Or we could even be really specific with CursorArea.

[DJMcNab]

The rename is the more important of the two, I agree; BoundingBox is a pretty good name here.

[nicoburns]

Renamed to BoundingBox

[nicoburns]

This turns out to have a nice compile time benefit for fontique (which people may well wish to use without using other parts of the linebender ecosystem - e.g. https://xi.zulipchat.com/#narrow/channel/296640-font-tech/topic/Refactoring.20fontique.20backend.20into.20separate.20crate).

peniko itself is quite lightweight, but it depends on color and kurbo which are both small-but-not-nothing.

[DJMcNab]

A few nits. Approval is conditional on them being applied

I would probably like to see a slightly expanded doc on bounding box (e.g. mentioning y-down space, talking about whether the values are logical pixels, etc.). But I'm not going to block on that.

I also think that this change does deserve a changelog entry, but again I'm not going to block on that.