cpp-common/bt2: make `getSupportedMipVersions` methods take a `ConstMapValue`

cpp-common/bt2: make `getSupportedMipVersions` methods take a `ConstMapValue`

The "get_supported_mip_versions" component class methods always receive
a map value.  The equivalent methods in the C++ bindings should
therefore take a `ConstMapValue.

Change-Id: Ia3ba17048337d3abb72cefa2ae88c7b3187833f2
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12048
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>