commit 8ccb3caa micro-optimized
page_id_t as a wrapper of uint64_t.

buf_dump_t: Remove, and replace with page_id_t, which uses
exactly the same encoding.

buf_page_info_t: Replace space_id,page_num with page_id_t id.

i_s_innodb_set_page_type(): Remove unnecessary code.
The buf_page_info_t::id was already assigned at the start
of the only caller, i_s_innodb_buffer_page_get_info().