Make Emacs respect string delimiter default (#6)

* [Emacs] Use default CLI options when nothing is specified

* [Emacs] expose setters and getters for request options

* lint: add rustfmt.toml and pass format

Using the configuration `tab_spaces = 2` to minimize the impact on
formatting src/emacs_wrapper.rs

* Backport 67924eefef

This is redone by using `saturating_add_signed` instead of having an
extra helper function. The function is stable since Rust 1.66

* Part 1 of compilation fixes

Upgrade to emacs crate 0.19

Fix all conversions to/from Lisp except the Vec<String> <-> Vector equivalence

Apparently one reference to env keeps escaping

* Fix compilation errors and few clippies

Author: gagbo