[llvm] [NFC] CoroElide: Refactor `Lowerer` into `CoroIdElider` (PR #91539)

[Chuanqi Xu via llvm-commits]

================
@@ -33,24 +33,46 @@ static cl::opt<std::string> CoroElideInfoOutputFilename(
 
 namespace {
 // Created on demand if the coro-elide pass has work to do.
-struct Lowerer : coro::LowererBase {
+class FunctionElideManager {
----------------
ChuanqiXu9 wrote:

The name seems not good. It doesn't manage anything. Maybe we can call it `*Info`

https://github.com/llvm/llvm-project/pull/91539