Missing provider shutdowns when setting new provider

[nicklasl]

When using the setProvider method(s), the previously set provider shutdown method is not called as defined in the spec: https://openfeature.dev/specification/sections/flag-evaluation/#requirement-1123

kotlin-sdk/kotlin-sdk/src/commonMain/kotlin/dev/openfeature/kotlin/sdk/OpenFeatureAPI.kt

Lines 99 to 100 in 91d60bc

	// TODO should we send shutdown to previous provider:
	// getProvider().shutdown()