feat: mf_dedup and associated test

tests/crossplatform/mf_dedup.test.sas

@@ -0,0 +1,23 @@
+/**
+  @file
+  @brief Testing mf_dedup macro
+
+  <h4> SAS Macros </h4>
+  @li mf_dedup.sas
+  @li mp_assert.sas
+
+**/
+
+%let str=One two one two and through and through;
+
+%mp_assert(
+  iftrue=("%mf_dedup(&str)"="One two one and through"),
+  desc=Basic test,
+  outds=work.test_results
+)
+
+%mp_assert(
+  iftrue=("%mf_dedup(&str,outdlm=%str(,))"="One,two,one,and,through"),
+  desc=Outdlm test,
+  outds=work.test_results
+)