Add tests

tests/cases/conformance/types/intersection/intersectionReduction.ts

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+// @strict
+
+declare const sym1: unique symbol;
+declare const sym2: unique symbol;
+
+type T1 = string & 'a';  // 'a'
+type T2 = 'a' & string & 'b';  // 'a' & 'b'
+type T3 = number & 10;  // 10
+type T4 = 10 & number & 20;  // 10 & 20
+type T5 = symbol & typeof sym1;  // typeof sym1
+type T6 = typeof sym1 & symbol & typeof sym2;  // typeof sym1 & typeof sym2
+type T7 = string & 'a' & number & 10 & symbol & typeof sym1;  // 'a' & 10 & typeof sym1
+
+type T10 = string & ('a' | 'b');  // 'a' | 'b'
+type T11 = (string | number) & ('a' | 10);  // 'a' | 10