Add collapse all and expand level buttons to conan report diff html output

[AbrilRBS]

Changelog: Feature: Add collapse all and expand level buttons to conan report diff html output.
Docs: Omit

Found this super useful for huge diffs when reviewing recipes in CCI, so along with filtering, it's easier to focus on the important files

To the inevitable question:

Expand level vs collapse all: Why not collapse level too? because it's harder to cleanly implement, and because this is what Idea does too