[perl #82111] de-pessimise some my @array = ...

[perl #82111] de-pessimise some my @array = ...

Due to obscure closure and goto tricks, it's sometimes possible for the
array or hash in the LHS of 'my @a = ...' and 'my %h = ...' to be
non-empty. At compile-time, these conditions are detected and the assign
op is compiled with the OPpASSIGN_COMMON, making the assignment slower.

This commit speeds it up again by adding a run-time check to pp_aassign
to only do the OPpASSIGN_COMMON code-branch if the LHS isn't an empty
array or hash.

See also #70171.