[clang] Mechanically port bulk of x86 builtins to TableGen (PR #120831)

[Chandler Carruth via cfe-commits]

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@@ -108,9 +109,15 @@ class PrototypeParser {
     } else if (T.consume_back("&")) {
       ParseType(T);
       Type += "&";
+    } else if (T.consume_front("long long")) {
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chandlerc wrote:

Sure, I use the Fish shell and have a bunch of command line tools that help with this installed:

- https://github.com/BurntSushi/ripgrep as `rg`, nicer form of `grep`
- https://github.com/chmln/sd as `sd`, nicer form of `sed` for line-based regex search and replace

Combined, they let me write a `diff` command like:

```fish
diff -u (rg -I '^(TARGET|BUILTIN)' BuiltinsX86.def BuiltinsX86.inc | sd '^BUILTIN\((.*)\)' 'TARGET_BUILTIN($1, "")' | sd ' +' ' ' | sd ',([X"])' ', $1' | sort | psub)  (rg '^TARGET' dev/tools/clang/include/clang/Basic/BuiltinsX86.inc | sort | psub)
```

Here `BuiltinsX86.def` and `BuiltinsX86.inc` are copies of the `.def` and `.inc` from before this PR, and `dev/tools/.../BuiltinsX86.inc` is the `.inc` produced in my development build.

All the uses of `sd` on the original `.def` and `.inc` files are to process away weird whitespace artifacts, and the use of `BUILTIN` instead of `TARGET_BUILTIN` in four places.

https://github.com/llvm/llvm-project/pull/120831