log substitution support for ssh and ssh-ng substituters

[symphorien]

Is your feature request related to a problem? Please describe.
I have a CI that builds store paths. Sometimes I want to fetch the log from another computer with nix log foo.drv --option substituters ssh-ng://remote.

Steps to reproduce:

# on the remote
$  nix-build -E 'with import <nixpkgs> {}; runCommand "foo" {} "echo foo; touch $out"'
this derivation will be built:
  /nix/store/h3r482pvxddrm6k51hdq7p2v73iwim8q-foo.drv
building '/nix/store/h3r482pvxddrm6k51hdq7p2v73iwim8q-foo.drv'...
foo
/nix/store/0c8l4igrdiw127iv5cyp53mnrsmk4lxk-foo
# locally
$ sudo nix --option experimental-features nix-command log /nix/store/h3r482pvxddrm6k51hdq7p2v73iwim8q-foo.drv --option substituters ssh-ng://remote
error: path '/nix/store/h3r482pvxddrm6k51hdq7p2v73iwim8q-foo.drv' is not a valid store path

Describe the solution you'd like
the ssh substitution protocol supports substituting logs, like the http one.

Describe alternatives you've considered

Additional context
related to but distinct from #5079

[Ericson2314]

I think the issue is logs are not really part of the store abstraction yet? They are sot of an ad-hoc concept thrown on for https and the CLI.

I think we should make logs / "build attempts" a first class concept. For floating CA derivations, they are 1-1 one with the set of rust mappings for each output! For other types of derivations, they don't latch onto an existing concept, but are still useful.

I thought i made an issue for this, but I cannot find it.