Improve macro hygiene

[siku2]

I keep running into places where Yew's macros aren't as hygienic as they could be. Especially now that the MSRV is 1.45.0 (which brings a few more macro features like mixed_site) it's time to do a full sweep and solve all the remaining issues:

• Ensure all trait methods are invoked unambiguously
• Use fully qualified paths everywhere (including primitives from ::std::primitive)
• Use a configurable yew crate parameter
• Use Span::mixed_site() for macro variables so they aren't available in user code
• Test with #![no_implicit_prelude]
  • html_macro
  • properties derive
  • props macro
  • classes macro
  • function component derive
• Add #[doc(hidden)] to all structs (especially in derive_props)

[mc1098]

Use a configurable yew crate parameter

Why not? :)

Use Span::mixed_site() for macro variables so they aren't available in user code

When I've tried to tackle this I find that either I have to lose out on a useful span for error messages - or jump through some hoops to still use a variable from one quote block to another. Not sure if I'm missing something here :) thought I'd mention why I have seemingly stopped chipping away at this issue 😅