[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/imports/ExplicitPackageImportsAmbiguity.fir.kt

@@ -0,0 +1,17 @@
+// FILE: a.kt
+package a.x
+
+class X
+
+// FILE: b.kt
+package b.x
+
+class X
+
+// FILE: c.kt
+package c
+
+import a.x
+import b.x
+
+class Y : x.X