Use (ice-9 binary-ports) instead of (rnrs io ports).

Use (ice-9 binary-ports) instead of (rnrs io ports).

This reduces the closure of (guix ui) from 123 to 106 modules.

* guix/derivations.scm: Use (ice-9 binary-ports) instead of (rnrs io
ports).
(map-derivation)[substitute-file]: Use 'read-string' instead of
'get-string-all'.
* guix/ftp-client.scm: Likewise.
* guix/hash.scm: Likewise.
* guix/http-client.scm: Likewise.
* guix/pki.scm (ensure-acl, current-acl): Likewise.
* guix/scripts/archive.scm (authorize-key)[read-key]: Likewise.
* guix/scripts/authenticate.scm (read-canonical-sexp)
(read-hash-data): Likewise.
* guix/scripts/download.scm: Likewise.
* guix/scripts/offload.scm (register-gc-root, remove-gc-roots)
(send-files): Likewise.
* guix/scripts/publish.scm (lazy-read-file-sexp): Likewise.
* guix/scripts/refresh.scm: Likewise.
* guix/scripts/substitute.scm (check-acl-initialized): Likewise.
* guix/serialization.scm (read-maybe-utf8-string): Likewise.
* guix/scripts/hash.scm (guix-hash): Use 'force-output' instead of
'flush-output-port'.
* guix/store.scm (process-stderr): Likewise.
* guix/tests.scm: Likewise.
* guix/utils.scm: Use (ice-9 binary-ports) and autoload (rnrs io ports)
for 'make-custom-binary-input-port'.