ComboBox: Move filtered options out of state

[jpuri]

FilteredOptions in ComboBox are derived from other state variables and should not be part of state. Also its creating this issue reported by @bvleur :

"If you arrive at a input value matching an option by pressing backspace, the isMatchingOption won't be set to true."

[jpuri]

Fix:
I do not wanted to move logic for calculation of filtered option in render method as that calculation may not be needed each time combobox is rendered. I have rather moved it to a variable (instance variable) of ComboBox, so that we calculate it only when:

1. Component is initialized or receives props.
2. Value of component changes.