[llvm] [llvm-objdump] print out xcoff file header and load section header for xcoff object file with option private-headers (PR #96350)

[James Henderson via llvm-commits]

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+## Test the --privated-headers option for XCOFF object files.
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jh7370 wrote:

```suggestion
## Test the --private-headers option for XCOFF object files.
```

https://github.com/llvm/llvm-project/pull/96350