GH-40026: [C++][FS][Azure] Add support for reading user defined metadata

[kou]

Rationale for this change

Users may want to set user defined metadata and/or properties such as Content-Type.

What changes are included in this PR?

• Write user defined metadata.
• But the following metadata are written as properties:
  • Content-Type
  • Content-Encoding
  • Content-Language
  • Content-Disposition
  • Cache-Control
• The following metadata is ignored because corresponding properties are auto generated:
  • Content-Hash

Are these changes tested?

Yes.

Are there any user-facing changes?

Yes.

• GitHub Issue: [C++][FS][Azure] Include user set metadata in ObjectInputFile::ReadMetadata #40026

[kou]

@Tom-Newton @felipecrv What do you think about this?

[github-actions]

⚠️ GitHub issue #40670 has been automatically assigned in GitHub to PR creator.

[Tom-Newton]

Looks good to me 🙂

I think there are actually 3 issues that this resolves: #40670, #40026, #40057

[github-actions]

⚠️ GitHub issue #40026 has been automatically assigned in GitHub to PR creator.

[kou]

Oh, I didn't notice that this is related to #40057. (I haven't read #40057 carefully, sorry.)

[kou]

I'll merge this in a few days if nobody objects this.

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 7 benchmarking runs that have been run so far on merge-commit fa36cde.

There were no benchmark performance regressions. 🎉

The full Conbench report has more details. It also includes information about 8 possible false positives for unstable benchmarks that are known to sometimes produce them.