[llvm] [CodeGen] Port WasmEHPrepare to new pass manager (PR #74435)

[Heejin Ahn via llvm-commits]

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@@ -88,10 +89,12 @@
 
 using namespace llvm;
 
-#define DEBUG_TYPE "wasmehprepare"
+#define DEBUG_TYPE "wasm-eh-prepare"
 
 namespace {
-class WasmEHPrepare : public FunctionPass {
+class WasmEHPrepareImpl {
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aheejin wrote:

What makes the current `WasmEHPrepare` class not sharable between the legacy and the new PM and why do we need the additional `Impl` class? 

https://github.com/llvm/llvm-project/pull/74435