[FIR] Add inline checker for bodies of inline functions

This checker doesn't support `@PublishedAPI` yet, so some BB tests for it
 were muted. #KT-46270

compiler/testData/diagnostics/tests/inline/functions.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE -UNNECESSARY_NOT_NULL_ASSERTION -UNNECESSARY_SAFE_CALL
 
 fun getFun(s: (p: Int) -> Unit): Function1<Int, Int> = {11}
@@ -9,4 +10,4 @@ inline fun testExtension(s: (p: Int) -> Unit) {
     getInlineFun(s).invoke(10)
     getInlineFun(s)!!.invoke(10)
     getInlineFun(s)?.invoke(10)
-}
+}