They are spread out into multiple files with different names.
Changes
* is_system_tablespace() -> fsp_is_system_or_temp_tablespace()  This function was used in about 30 places and is confusing because it checks for both types of predefined system tablespaces.  Some of the places it was used is only concerned with ibdata, which is often specifically called the system tablespace.
* srv_is_undo_tablespace() -> fsp_is_undo_tablespace()  moved this function to fsp0fsp.cc and fsp0types.h with all the others
* Tablespace::is_undo_tablespace() -> fsp_is_undo_tablespace()
* (space == srv_sys_space.space_id) -> (space_id == TRX_SYS_SPACE) simpler to understand and quicker inline, and srv_sys_space will never use any other space_id than 0
* fil_is_user_tablespace_id() -> fsp_is_ibd_tablespace() and moved to fsp0fsp.cc.  The 'user' reference is vague since system and temp spaces can contain user data.
* Used dict_table_is_file_per_table() where the same condition exists and where it is more appropriate.
* Used fsp_is_file_per_table() where the same condition exists.
* Deleted is_system_or_undo_tablespace() because it was unclear what the 'system' meant.  In this case it did not include the temp tablespace.  Replaced it with 	    (space == TRX_SYS_SPACE || fsp_is_undo_tablespace(space))
* Calls to trx_rseg_mem_create(() will ALWAYS use univ_page_size.  undo, temp and system tablespaces that contain rollback segments are always univ_page_size. Deleted code that searched for the page size of system tablespaces. Asserted in trx0rseg.cc where the space->flags were readily available.
* Used fsp_is_system_temporary() in about a dozen places where a space_id was compared directly to srv_tmp_space.space_id()

Approved by Vasil in rb#14093.