`g:rustfmt_autosave` doesn't save folds on `:w`

[whereistejas]

Hi,
Currently, :RustFmt discards all folds when it autoformats any files.

rust.vim version.

master

Steps to reproduce:

1. Set g:rustfmt_autosave to true in vim config.
2. Open any rust file and open a fold.
3. Save that file using :w.
4. You will notice that fold has been discarded.

Expected vs. actual behavior:

Ideally, these folds should be saved.

Related issues/issues that can be referenced

fatih/vim-go#691

RustInfo

rust.vim Global Variables:
let g:ftplugin_rust_source_path = v:null
let g:loaded_syntastic_rust_cargo_checker = v:null
let g:loaded_syntastic_rust_filetype = v:null
let g:loaded_syntastic_rust_rustc_checker = v:null
let g:rust_bang_comment_leader = v:null
let g:rust_cargo_avoid_whole_workspace = v:null
let g:rust_clip_command = v:null
let g:rust_conceal = v:null
let g:rust_conceal_mod_path = v:null
let g:rust_conceal_pub = v:null
let g:rust_fold = v:null
let g:rust_last_args = v:null
let b:rust_last_args = []
let g:rust_last_rustc_args = v:null
let b:rust_last_rustc_args = []
let g:rust_original_delimitMate_excluded_regions = v:null
let g:rust_playpen_url = v:null
let g:rust_prev_delimitMate_quotes = v:null
let g:rust_recent_nearest_cargo_tol = v:null
let g:rust_recent_root_cargo_toml = v:null
let g:rust_recommended_style = v:null
let g:rust_set_conceallevel = v:null
let g:rust_set_conceallevel=1 = v:null
let g:rust_set_foldmethod = v:null
let g:rust_set_foldmethod=1 = v:null
let g:rust_shortener_url = v:null
let g:rustc_makeprg_no_percent = v:null
let g:rustc_path = v:null
let g:rustfmt_autosave = 0
let g:rustfmt_autosave_if_config_present = v:null
let g:rustfmt_command = 'rustfmt'
let g:rustfmt_emit_files = 1
let g:rustfmt_fail_silently = 0
let g:rustfmt_options = ''
let g:syntastic_extra_filetypes = ['rust']
let g:syntastic_rust_cargo_fname = v:null
rustfmt 1.4.37-stable (2a3635d 2021-05-04)
rustc 1.53.0 (53cb7b09b 2021-06-17)
cargo 1.53.0 (4369396ce 2021-04-27)

NVIM v0.6.0-dev+1639-g50b30de20
Build type: Debug
LuaJIT 2.1.0-beta3