Simplified `lf -remote` interface

[c4rlo]

#2145 got me thinking that it would be quite nice if there was a simpler way to send commands to the current (in the sense of $id) lf instance.

A typical example from https://github.com/gokcehan/lf/wiki/Integrations illustrates this:

cmd zi ${{
    result="$(zoxide query -i | sed 's/\\/\\\\/g;s/"/\\"/g')"
    lf -remote "send $id cd \"$result\""
}}

The need for manually quoting the result is quite cumbersome.

I'd like to be able to instead write this as:

cmd zi ${{
    result=$(zoxide query -i)
    lf -local-send cd "$result"
}}

So, my proposal is to introduce new command-line options as follows:

1. lf -local-send COMMAND ARGS... shall be equivalent to lf -remote "send $id COMMAND ARGS...", but taking care of the quoting.
2. lf -local-query TYPE shall be similarly equivalent to lf -remote "query $id TYPE".

Note that these commands would require the id environment variable to be set.

Further options and variations that may be considered:

• It may then be reasonable to rename the id environment variable to something more unique, e.g. lf_id (with a period of backward compatibility). Once there is less need to type it out, it's fine if it's a few characters longer.
• Does query really need to be its own special thing, or could that just be a built-in command?
• I'm combining two ideas here – not needing to spell out $id and taking care of quoting – but they are kind of independent. Could do only one or the other.

[joelim-work]

A simplified syntax like lf -send cd /some/path sounds appealing at first, but I think will only work well for specific scenarios like cding to a particular directory, and not so well for others:

• The syntax lf -send COMMAND [ARGS]... can really only support read commands. Other types of commands like shell commands ($vim) or list commands (:toggle; down) don't fit, although it could be possible to add an eval command which evaluates a string and executes it similar to how the source command works.
• Arguments would be passed as literal strings without processing escape sequences, so echo foo\tbar would print literally foo\tbar and not foo<tab>bar.

An idea you could try is to write a wrapper command that builds the string to be executed and then pass it to lf -remote.