crimson/os/seastore: add ExtentIndex::clear_and_dispose

crimson/os/seastore: add ExtentIndex::clear_and_dispose

When a transaction is interrupted and needs to repeat, its reset_preserve_handle() method
is called to clear various extent set and list. The problem is the clear operation call
ExtentIndex::clear() instead of ExtentIndex::erase(), which would leave CachedExtent::parent_index
still pointing to the write_set/delayed_set while the CachedExtent is no longer linked to
those sets. This would make CachedExtent::~CachedExtent() to try to erase itself from
CachedExtent::parent_index even it's not linked, which would cause failures in the successive
operations

Signed-off-by: Xuehan Xu <xxhdx1985126@gmail.com>