Unify type conversion functions in ShaderNode

[LeviPesin]

Related issue: -

Description

Unified type conversion functions in the ShaderNode.

[LeviPesin]

Actually, maybe it is even better to move the code

if ( ( params.length === 1 ) && ( valueComponents !== 1 ) ) {

	// Providing one scalar value: This value is used for all components

	for ( let i = 1; i < valueComponents; i ++ ) {

		params[ i ] = params [ 0 ];

	}

}

to the corresponding .set() methods of different classes? E.g. make so that if Vector2.set() method is given one argument, it sets both components to that value (with something like if ( y === undefined ) { y = x }).

[sunag]

Thanks!!