Up to 6 Tramming points (#20720)

Marlin/src/feature/tramming.cpp

   PGMSTR(point_name_4, TRAMMING_POINT_NAME_4);
   #ifdef TRAMMING_POINT_NAME_5
     PGMSTR(point_name_5, TRAMMING_POINT_NAME_5);
+    #ifdef TRAMMING_POINT_NAME_6
+      PGMSTR(point_name_6, TRAMMING_POINT_NAME_6);
+    #endif
   #endif
 #endif
 
     , point_name_4
     #ifdef TRAMMING_POINT_NAME_5
       , point_name_5
+      #ifdef TRAMMING_POINT_NAME_6
+        , point_name_6
+      #endif
     #endif
   #endif
 };

Marlin/src/feature/tramming.h

 constexpr xy_pos_t screws_tilt_adjust_pos[] = TRAMMING_POINT_XY;
 
 #define G35_PROBE_COUNT COUNT(screws_tilt_adjust_pos)
-static_assert(G35_PROBE_COUNT >= 3, "TRAMMING_POINT_XY requires at least 3 XY positions.");
+static_assert(WITHIN(G35_PROBE_COUNT, 3, 6), "TRAMMING_POINT_XY requires between 3 and 6 XY positions.");
 
 #define VALIDATE_TRAMMING_POINT(N) static_assert(N >= G35_PROBE_COUNT || Probe::build_time::can_reach(screws_tilt_adjust_pos[N]), \
   "TRAMMING_POINT_XY point " STRINGIFY(N) " is not reachable with the default NOZZLE_TO_PROBE offset and PROBING_MARGIN.")
-VALIDATE_TRAMMING_POINT(0); VALIDATE_TRAMMING_POINT(1); VALIDATE_TRAMMING_POINT(2); VALIDATE_TRAMMING_POINT(3); VALIDATE_TRAMMING_POINT(4);
+VALIDATE_TRAMMING_POINT(0); VALIDATE_TRAMMING_POINT(1); VALIDATE_TRAMMING_POINT(2); VALIDATE_TRAMMING_POINT(3); VALIDATE_TRAMMING_POINT(4); VALIDATE_TRAMMING_POINT(5);
 
 extern const char point_name_1[], point_name_2[], point_name_3[]
   #ifdef TRAMMING_POINT_NAME_4
     , point_name_4[]
     #ifdef TRAMMING_POINT_NAME_5
       , point_name_5[]
+      #ifdef TRAMMING_POINT_NAME_6
+        , point_name_6[]
+      #endif
     #endif
   #endif
 ;
     #ifdef TRAMMING_POINT_NAME_5
       #undef _NR_TRAM_NAMES
       #define _NR_TRAM_NAMES 5
+      #ifdef TRAMMING_POINT_NAME_6
+        #undef _NR_TRAM_NAMES
+        #define _NR_TRAM_NAMES 6
+      #endif
     #endif
   #endif
 #endif