Make tt generic over the span data
This also fixes up our delimiter representation in tt, it is no longer optional (we use invisible delims in the same way as before, that is still incorrectly) and we now store two spans instead of one.
These changes should help with adjusting our token map. Though this will probably break proc-macros in some ways, will need to test that for now.
feat: Remove support for 1.58 proc-macro abi
This seems old enough that we can drop the support for it now, the less ABIs we have the less work it is adjusting our span implementation.
Extracted from https://github.com/rust-lang/rust-analyzer/pull/14061, will rebase that over this once merged.
feat: Improve "match to let else" assist
Closes https://github.com/rust-lang/rust-analyzer/issues/13540
Handles complex `let` patterns (rather than just idents), and diverging block expressions have their `{`/`}` stripped to create nicer code.
Update documentation for emacs and split it for LSP-mode and Eglot
Emacs has now two LSP clients, the more minimalistic and lightweight [Eglot](https://joaotavora.github.io/eglot) and the extensive though a bit bloated [LSP Mode](https://github.com/emacs-lsp/lsp-mode). Eglot will soon be shipped with Emacs29. Both have rust-analyzer enabled by default and require no further setup other then being installed and enabled. `lsp-rust.el` is not required anymore.
The base-installation for each of those modes is so easy now that I don't think an enumerated list is necessary, both packages can be installed via the standard `M-x package-install` and the installation is a one-liner that I provide.
Configuration is only necessary for supporting the rust-analyzer extensions to the LSP protocol, which are built into LSP mode and require an [extension-package](https://github.com/nemethf/eglot-x) for Eglot.
But for further documentation, including the LSP extensions, I link against official documentation where possible to avoid duplicating efforts having to continually update this to stay up-to-date.
I rewrote most of the original emacs documentation, but the [linked blog](https://robert.kra.hn/posts/2021-02-07_rust-with-emacs/) post by `@rksm` seems still being actively updated with updates to LSP mode, so I kept the link. That blog post is opinionated, I personally use different packages which achieve similar end results (Eglot instead of LSP-mode, corfu instead of capf, vertico instead of helm etc.). But if someone doesn't already have an extensive Emacs configuration, I think this is not a bad starting point.
Disclaimer: I'm a Rust beginner, which is why I read the rust-analyzer setup docs. So I necessarily know how most Rust experts use Emacs. But I'm an experienced Emacs user who uses several other programming languages via LSP-mode support in Emacs. I used both, initially LSP-mode and recently migrated to Eglot.
Also I'm not an experienced in writing asciidoc and I didn't do a local test-built, hopefully the html builds in the way I imagine it. So I recommend to check that aspect of the PR. Maybe the documentation is in the CI build-artifacts?
This is a duplicate of a PR to the old rust-analyzer project https://github.com/rust-analyzer/rust-analyzer.github.io/pull/197, which I made because I didn't know that the documentation now lives here.
