Change 'isSpecified*' & 'isIntrospectionType' accept only correct types

[IvanGoncharov]

Fixes #2153
Previous disscussion: #1837 (comment)

[IvanGoncharov]

An alternative solution to #2194
I feel like we made a mistake in designing isSpecifiedDirective, isSpecifiedScalarType and isIntrospectionType predicates because we mixed type refinement and value refinement. For example in case of isSpecifiedScalarType we are mixing type instanceof GraphQLScalarType(refines type) and type.name === ...(refines value).
So I think #2153 is not unique to TS but a symptom of the general problem here.

@tgriesser Would be great to get your opinion?
@Cito We already discussed isSpecifiedDirective in #1837 would be great to get your opinion on this change?

[IvanGoncharov]

Also, we have other value predicates for example isRequeiredArgument:

graphql-js/src/type/definition.js

Lines 944 to 946 in ed0dfe8

	export function isRequiredArgument(arg: GraphQLArgument): boolean %checks {
	return isNonNullType(arg.type) && arg.defaultValue === undefined;
	}

graphql-js/src/type/definition.js

Lines 1464 to 1468 in ed0dfe8

	export function isRequiredInputField(
	field: GraphQLInputField,
	): boolean %checks {
	return isNonNullType(field.type) && field.defaultValue === undefined;
	}