input: qmp_send_key(): simplify

input: qmp_send_key(): simplify

The current code duplicates the QKeyCodeList keys in order to store
the key values for release_keys() late run. This is a bit complicated
though, as we have to care about correct ordering and then release_keys()
will have to index key_defs[] over again.

Switch to an array of integers, which is dynamically allocated and stores
the already converted key value.

This simplifies the current code and the next commit.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>