Rework raid self/group frame visibility and rename the solo option

- selfinraid now gates on `not IsInGroup()`, so "show self in raid frames"
  applies only when truly solo (both party and raid suppress it), matching
  the option's actual behavior.
- Hide the redundant group frames when a party is promoted to the raid grid
  (raidforgroup + hide_in_raid), not just in an actual raid. A shared
  hide_group local drives both the party-member and self branches; the
  party-member branch is scoped to cache_raid == 0 so the raidforgroup-mapped
  raid frames (which themselves carry label "party") aren't hidden too.
- Rename "Always Show Self In Raid Frames" to "Show Self In Raid Frames When
  Solo" in gui.lua and all locale files; the four previously-translated
  strings are reset to nil stubs since the meaning changed.

env/translations_deDE.lua

@@ -27,7 +27,6 @@ pfUI_translation["deDE"] = {
   ["Always Show Item Comparison"] = nil,
   ["Always Show On Target Units"] = nil,
   ["Always Show On Units With Missing HP"] = nil,
-  ["Always Show Self In Raid Frames"] = nil,
   ["Always Use 2D Portraits"] = nil,
   ["Ammo Counter"] = nil,
   ["Anchor Bags Above Chat"] = nil,
@@ -741,6 +740,7 @@ pfUI_translation["deDE"] = {
   ["Show Required Questitem Count"] = nil,
   ["Show Resting"] = nil,
   ["Show Self In Group Frames"] = nil,
+  ["Show Self In Raid Frames When Solo"] = nil,
   ["Show Spell Icon"] = nil,
   ["Show Spell Name"] = nil,
   ["Show Stacks"] = nil,