We have a lot of places in the code where
a token_metadata_ptr is kept in an automatic
variable and destroyed when it leaves the scope.
since it's a referenced counted lw_shared_ptr,
the token_metadata object is rarely destroyed in
those cases, but when it is, it doesn't go through
clear_gently, and in particular its tablet_metadata
is not cleared gently, leading to inefficient destruction
of potentially many foreign_ptr:s.
This patch calls clear_and_destroy_impl that gently
clears and destroys the impl object in the background
using the shared_token_metadata.
Fixes#13381
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
2c0bafb934