qga: Replace 'blacklist' command line and config file options by 'block-rpcs'

Let's use a more appropriate wording for this command line and config
file option. The old ones are still accepted for compatibility reasons,
but marked as deprecated now so that it could be removed in a future
version of QEMU.

This change is based on earlier patches from Philippe Mathieu-Daudé,
with the idea for the new option name suggested by BALATON Zoltan.

And while we're at it, replace the "?" in the help text with "help"
since that does not have the problem of conflicting with the wildcard
character of the shells.

Message-Id: <20220727092135.302915-2-thuth@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

docs/about/deprecated.rst

@@ -370,3 +370,22 @@ be deleted from this tree.
 New deployments should use the Rust version, and existing systems
 should consider moving to it.  The command line and feature set
 is very close and moving should be simple.
+
+
+QEMU guest agent
+----------------
+
+``--blacklist`` command line option (since 7.2)
+'''''''''''''''''''''''''''''''''''''''''''''''
+
+``--blacklist`` has been replaced by ``--block-rpcs`` (which is a better
+wording for what this option does). The short form ``-b`` still stays
+the same and thus is the preferred way for scripts that should run with
+both, older and future versions of QEMU.
+
+``blacklist`` config file option (since 7.2)
+''''''''''''''''''''''''''''''''''''''''''''
+
+The ``blacklist`` config file option has been renamed to ``block-rpcs``
+(to be in sync with the renaming of the corresponding command line
+option).