[llvm] [NFC] Add fragment-getting functions to DbgRecord (PR #97705)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `polly-x86_64-linux-shlib` running on `polly-x86_64-gce2` while building `llvm` at step 5 "build".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/99/builds/575

Here is the relevant piece of the build log for the reference:
```
Step 5 (build) failure: 'ninja' (failure)

```

https://github.com/llvm/llvm-project/pull/97705