MDEV-8360 Clean-up CHARSET_INFO: strnncollsp: diff_if_only_endspace_difference

- Removing the "diff_if_only_endspace_difference" argument from
  MY_COLLATION_HANDLER::strnncollsp(), my_strnncollsp_simple(),
  as well as in the function template MY_FUNCTION_NAME(strnncollsp)
  in strcoll.ic

- Removing the "diff_if_only_space_different" from ha_compare_text(),
  hp_rec_key_cmp().

- Adding a new function my_strnncollsp_padspace_bin() and reusing
  it instead of duplicate code pieces in my_strnncollsp_8bit_bin(),
  my_strnncollsp_latin1_de(), my_strnncollsp_tis620(),
  my_strnncollsp_utf8_cs().

- Adding more tests for better coverage of the trailing space handling.

- Removing the unused definition of HA_END_SPACE_ARE_EQUAL

include/my_base.h

@@ -298,11 +298,7 @@ enum ha_base_keytype {
 #define HA_SWAP_KEY		 64
 #define HA_REVERSE_SORT		 128	/* Sort key in reverse order */
 #define HA_NO_SORT               256 /* do not bother sorting on this keyseg */
-/*
-  End space in unique/varchar are considered equal. (Like 'a' and 'a ')
-  Only needed for internal temporary tables.
-*/
-#define HA_END_SPACE_ARE_EQUAL	 512
+
 #define HA_BIT_PART		1024
 #define HA_CAN_MEMCMP           2048 /* internal, never stored in frm */