[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/lambdaCast.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNCHECKED_CAST -USELESS_CAST
 inline public fun reg(convertFunc: (Any) -> Any) {
     convertFunc("")
@@ -6,4 +7,4 @@ inline public fun reg(convertFunc: (Any) -> Any) {
 public inline fun <reified T : Any, reified R : Any> register(converter: (T) -> R) {
     <!USAGE_IS_NOT_INLINABLE!>converter<!> as (Any) -> Any
     reg(<!USAGE_IS_NOT_INLINABLE!>converter<!> as (Any) -> Any)
-}
+}