[llvm] [CodeGen] Represent ISD::ArgFlagsTy flags as a bitmask (NFC) (PR #217548)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `sanitizer-aarch64-linux-fuzzer` running on `sanitizer-buildbot12` while building `llvm` at step 2 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/159/builds/53671

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 2 (annotate) failure: 'python ../sanitizer_buildbot/sanitizers/zorg/buildbot/builders/sanitizers/buildbot_selector.py' (failure)


```

</details>

https://github.com/llvm/llvm-project/pull/217548