change `+format--lsp-fn` to run `+format--lsp-fn` in context of main
buffer rather than apheleia's scratch buffer so that the lsp mode can
be discovered
BREAKING CHANGE: This commit introduces two changes, a breaking, one
not.
The breaking change: `+format-with-lsp` used to control lsp-mode/eglot
integration for this module, but it is now gated behind a new +lsp flag.
Users will need to add it to their `doom!` blocks (in $DOOMDIR/init.el)
to restore the integration.
The other change: I've merged the former `lsp` and `eglot` formatters
into a single `lsp` formatter that dispatches to the appropriate
backend, as well as wrapping this integration in a
`+format-with-lsp-mode` minor mode, so it can be toggled at will; mainly
to assist in debugging formatter behavior.
A unified formatter makes it easier for folks to configure
`+format-with` on a per-project/directory/file basis, without needing to
know what backend this module uses, and opens us up to integrating other
LSP backends in the future (like lsp-bridge).
