[Bug Fix] Fix Bot Creation Issue (#4235)

# Notes
- Creating bots was failing because were checking for `false` on `Database::CheckUsedName()` in `BotDatabase::QueryNameAvailability`.
- `Database::CheckUsedName()` is now `Database::IsNameUsed()` and checks for both bots and character name usages.
- We were checking for `false` which was always happening when there were no entries for the supplied name, meaning we were never allowed to create a bot.

zone/client.cpp

@@ -2228,8 +2228,8 @@ void Client::ChangeLastName(std::string last_name) {
 bool Client::ChangeFirstName(const char* in_firstname, const char* gmname)
 {
 	// check duplicate name
-	bool usedname = database.CheckUsedName((const char*) in_firstname);
-	if (!usedname) {
+	bool used_name = database.IsNameUsed((const char*) in_firstname);
+	if (used_name) {
 		return false;
 	}