[FIR JS] KT-57601: Get rid of the builtin provider

In this example we get 2 variants of `kotlin/toString()`:
one coming from the KLib provider, and the
other coming from the builtins provider.
These are identical deserialized functions.

^KT-57601 Fixed

compiler/testData/cli/js/successfulHmpp.args

@@ -14,3 +14,5 @@ fir-hmpp
 -Xfragment-sources=c\:$TESTDATA_DIR$/../jvm/hmpp/src/c.kt
 -Xfragment-refines=b\:a
 -Xfragment-refines=c\:b
+-libraries
+libraries/stdlib/js-ir/build/classes/kotlin/js/main