[Bug] Item Purchase Offset when multiple buyers are buying at the same time. (#4628)

* [Bug] Item Purchase Offset when multiple buyers are buying at the same time.

- Much of the code lifted from TAKP/P2002 and adapted
- Needs Testing
- This should help prevent situations where multiple people are purchasing items from a merchant and both attempt to purchase the same temp merchant or limited item, it should result in the later person recieving a notice that the item no longer exists and refreshes the merchant table.
- Updated strings

* fix formatting

* Push

* Update client.cpp

* Update database_update_manifest.cpp

* Update database_update_manifest.cpp

* Update database_update_manifest.cpp

* Update client.cpp

---------

Co-authored-by: Kinglykrab <kinglykrab@gmail.com>
Co-authored-by: Akkadius <akkadius1@gmail.com>

zone/mob.cpp

@@ -493,6 +493,8 @@ Mob::Mob(
 	m_AllowBeneficial = false;
 	m_DisableMelee    = false;
 
+	SetMerchantSessionEntityID(0);
+
 	for (int i = 0; i < EQ::skills::HIGHEST_SKILL + 2; i++) {
 		SkillDmgTaken_Mod[i] = 0;
 	}