all: move -panic=trap support to the compiler/runtime

Support for `-panic=trap` was previously a pass in the optimization
pipeline. This change moves it to the compiler and runtime, which in my
opinion is a much better place.

As a side effect, it also fixes
https://github.com/tinygo-org/tinygo/issues/4161 by trapping inside
runtime.runtimePanicAt and not just runtime.runtimePanic.

This change also adds a test for the list of imported functions. This is
a more generic test where it's easy to add more tests for WebAssembly
file properties, such as exported functions.

transform/testdata/panic.ll

@@ -1,22 +0,0 @@
-target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
-target triple = "armv7m-none-eabi"
-
-@"runtime.lookupPanic$string" = constant [18 x i8] c"index out of range"
-
-declare void @runtime.runtimePanic(ptr, i32)
-
-declare void @runtime._panic(i32, ptr)
-
-define void @runtime.lookupPanic() {
-  call void @runtime.runtimePanic(ptr @"runtime.lookupPanic$string", i32 18)
-  ret void
-}
-
-; This is equivalent to the following code:
-;     func someFunc(x interface{}) {
-;         panic(x)
-;     }
-define void @someFunc(i32 %typecode, ptr %value) {
-  call void @runtime._panic(i32 %typecode, ptr %value)
-  unreachable
-}

transform/testdata/panic.out.ll

@@ -1,25 +0,0 @@
-target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
-target triple = "armv7m-none-eabi"
-
-@"runtime.lookupPanic$string" = constant [18 x i8] c"index out of range"
-
-declare void @runtime.runtimePanic(ptr, i32)
-
-declare void @runtime._panic(i32, ptr)
-
-define void @runtime.lookupPanic() {
-  call void @llvm.trap()
-  call void @runtime.runtimePanic(ptr @"runtime.lookupPanic$string", i32 18)
-  ret void
-}
-
-define void @someFunc(i32 %typecode, ptr %value) {
-  call void @llvm.trap()
-  call void @runtime._panic(i32 %typecode, ptr %value)
-  unreachable
-}
-
-; Function Attrs: cold noreturn nounwind
-declare void @llvm.trap() #0
-
-attributes #0 = { cold noreturn nounwind }