Prevents solar panel assemblies from being anchored on an occupied tile or on each other (#91613)

## About The Pull Request

Title; should cover any impassable structures like machinery as well as
anchoring multiple assemblies on the same tile - it's already useless
since constructing the solar panel further already checks for other
solar panels on the tile (made that check more robust as well).
Squashed a case where a solar tracker would not assimilate the solar
assembly used for its construction, which would let you get more
assemblies with tracker electronics for nefarious purposes (duplication
is bad okay).
Some maps place solar panels on catwalks instead of fancy solar panel
tiling. For the purposes of a solar panel operation this is sufficient,
since a catwalk can support wiring. However, a solar assembly wasn't
accepting catwalks as a proper tile for anchoring. I see little reason
to disallow catwalks, so I made them work for anchoring assemblies.
Also makes use of balloon alerts for some of the stuff.

## Why It's Good For The Game

Fixes #79220
Consistency good. Duplication bad. Balloon alerts make monkey brain
happy.

## Changelog

🆑
fix: fixed being able to anchor multiple solar panel assemblies on a
single tile (or any dense tile for that matter)
fix: fixed solar trackers not absorbing the assembly upon construction,
leading to assembly duplication
qol: solar assemblies can be wrenched on catwalks
/🆑

code/modules/power/solar.dm

@@ -313,10 +313,21 @@
 	randomise_offset(anchored ? 0 : random_offset)
 
 /obj/item/solar_assembly/attackby(obj/item/item_used, mob/user, list/modifiers, list/attack_modifiers)
+	var/turf/solarturf = get_turf(src)
+
 	if(item_used.tool_behaviour == TOOL_WRENCH && isturf(loc))
-		if(isinspace())
-			to_chat(user, span_warning("You can't secure [src] here."))
+		if(!solarturf.can_have_cabling()) //allows catwalks
+			balloon_alert(user, "can't secure in space!")
 			return
+		for(var/obj/stuff_in_the_way in solarturf) //prevent anchoring on other machinery or solar assemblies
+			if(stuff_in_the_way == src)
+				continue
+			if(istype(stuff_in_the_way, /obj/item/solar_assembly) && stuff_in_the_way.anchored)
+				balloon_alert(user, "secured assembly in the way!")
+				return
+			if((stuff_in_the_way.density) && !(stuff_in_the_way.flags_1 & ON_BORDER_1))
+				balloon_alert(user, "something in the way!")
+				return
 		set_anchored(!anchored)
 		user.visible_message(
 			span_notice("[user] [anchored ? null : "un"]wrenches the solar assembly[anchored ? " into place" : null]."),
@@ -333,6 +344,10 @@
 			user.visible_message(span_notice("[user] takes out the electronics from the solar assembly."), span_notice("You take out the electronics from the solar assembly."))
 			return TRUE
 
+		//prevent construction if something dense's on our tile
+		if(solarturf.is_blocked_turf(exclude_mobs = TRUE, source_atom = src))
+			balloon_alert(user, "something in the way!")
+			return
 		if(!istype(item_used, /obj/item/stack/sheet/glass))
 			to_chat(user, span_warning("The tracker only accepts standard, un-reinforced glass."))
 			return
@@ -342,8 +357,8 @@
 			return
 		playsound(src.loc, 'sound/machines/click.ogg', 50, TRUE)
 		user.visible_message(span_notice("[user] places the glass on the solar assembly."),span_notice("You place the glass on the solar assembly."))
-		new /obj/machinery/power/tracker/(get_turf(src))
-		return
+		new /obj/machinery/power/tracker/(get_turf(src), src)
+		return TRUE
 
 	if(!tracker)
 		if(istype(item_used, /obj/item/electronics/tracker))
@@ -371,9 +386,9 @@
 		//an else statement can be put here if you want something to happen to all the misc items that make it this far
 		return
 
-	var/turf/solarturf = get_turf(src)
-	if(locate(/obj/machinery/power/solar) in solarturf)
-		to_chat(user, span_warning("A solar panel is already assembled here."))
+	//prevent construction if something dense's on our tile
+	if(solarturf.is_blocked_turf(exclude_mobs = TRUE, source_atom = src))
+		balloon_alert(user, "something in the way!")
 		return
 
 	if(is_glass_sheet(item_used))