We ended up converting this to a `Gfx::FloatPoint` in all but one place
any way so this just skips some extra handling and `Vector` allocations.
Also makes `parse_coordinate_pair_{double|triplet}` return `Vectors`
store data inline to avoid a heap alloc.
Previously we had a single `PathInstruction` struct which stored it's
data in a `Vector<float>`. We now define `PathInstruction` as a
`Variant<>` of structs storing data inline (note that the remaining
`Vector` properties will be replaced with `Gfx::FloatPoint` in a future
commit) - this avoids a `Vector` allocation and avoids magic indices
when accessing data.
This updates dumping to reflect the fact that each instruction only ever
contains a single set of arguments, and that `ClosePath` does not have a
concept of absoluteness (i.e. 'Z' and 'z' are equivalent).
More things need this than just the `<path>` element, so let's avoid
having to include `SVGPathElement.h` in places that don't need it.
Minor changes at the same time:
- Wrap it in a Path class
- Specify underlying type for PathInstructionType
- Make a couple of free functions into methods
- Give PathInstruction an operator==
No functionality changes.
