Stability hotfix for overrides

[psiberx]

• Fixed random crashes for very frequently called overrides (such as GameObject.OnGameAttached and GameObject.OnDetach on game reload).
• Fixed random crashes for hotkeys and inputs (for example, binding the mouse wheel had a very high chance of causing crashes).
• Fixed potential issues when CET mods that modify TweakDB are used with TweakDBext mods at the same time.
• Added the ability to add new free flats to TweakDB.

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With more extensive use of overrides a new issue was discovered: the Lua stack could be corrupted because TiltedPhoques::Vector<sol::object> args; was placed before acquiring the lock chain.pScripting->GetState() allowing another thread in the multithreaded environment to perform garbage collection, call Lua functions, and corrupt references in args.

This leads to two possible outcomes based on what's currently on the Lua stack:

• A call to sol::make_objec() cannot push a new value onto the stack and throw.
• The elements of the args refer to random values on the stack and call->ScriptFunction(as_args(args)) passes the random values to the Lua handler.