In a noninteractive shell, asynchronous commands ignore SIGINT and
SIGQUIT. We typically use such shells to feed fifo buffers which we
do want to cancel them on Control-C.  Make it so.

Same for SIGQUIT; that one is not typically used but I expect that
along the Kakoune server it kills any child processes that (haven't
been daemonized).

Note that for unknown reasons, Bash already doesn't ignore SIGINT in
async processes that use "eval".

Note that Dash has a bug that prevents this from working;
proposed fix is at
https://lore.kernel.org/dash/20240329153905.154792-2-aclopte@gmail.com/

(While at it balance out some parens, to help the m command)

When calling `:gopls definition`, the gopls LSP server returns the location of
the selected definition. Then, `gopls.kak` tries to parse this output to
feed the `:edit` command and open the file in Kakoune. To do this, it
uses `sed` to transform `<path>.go:<line>:<colstart>-<colend>` to `<path>.go
<line> <colstart>`. However, if the `<path>` contains a dash character,
the `sed` will fail and strip everything after this first dash, removing
the line and columns information.

Closes #4776

Co-authored-by: Frank LENORMAND <1379068+lenormf@users.noreply.github.com>

Remove unnecessary single quotes and whitespaces in %file{}
Do not delete error file before sending to debug buffer
Fix gopls definition error handling and empty sting check
Silence shellcheck warnings

Working functions replaced by gopls
Use kak-lsp if you need in place documentation and autocompletion

Add support for the following gopls commands:
 - format
 - imports
 - definition
 - references

Thanks krobelus@ and lenormf@ for their review and suggestions.

On the instances with altfile this was already the case, but this makes it more obvious.

Closes #3673

Closes #2783