Fixed an issue with parallel region reentrancy

[Andarist]

fixes https://discord.com/channels/795785288994652170/809564609383890965/986216911459209226

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Latest commit: 5386d60

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Name	Type
xstate	Patch

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[Andarist]

Since I've added another situation in which transition.entrySet might be mutated I had to make a copy here to avoid configuration being affected by this mutation. This was required by this test:

xstate/packages/core/test/actions.test.ts

Lines 715 to 735 in 1eff5ca

	it('should call each exit handler only once when the service gets stopped', () => {
	const actual: string[] = [];
	const machine = createMachine({
	exit: () => actual.push('root'),
	initial: 'a',
	states: {
	a: {
	exit: () => actual.push('a'),
	initial: 'a1',
	states: {
	a1: {
	exit: () => actual.push('a1')
	}
	}
	}
	}
	});
	interpret(machine).start().stop();
	expect(actual).toEqual(['a1', 'a', 'root']);
	});

Without this line it was calling exit actions multiple times as the mutated configuration contained duplicated state nodes