GH-40562: [C++] Repair FileSystem merge error

[bkietz]

Rationale for this change

Failure to rebase and build when merging #39067 (which renamed internal::Uri -> util::Uri) led to a merge conflict since #40325 added more usages of internal::Uri

What changes are included in this PR?

Rename internal::Uri -> util::Uri

Are these changes tested?

Yes

Are there any user-facing changes?

No

• GitHub Issue: [C++] Merge conflict with AzureFS changes #40562

[kou]

+1

[conbench-apache-arrow]

After merging your PR, Conbench analyzed the 7 benchmarking runs that have been run so far on merge-commit eecd779.

There were 2 benchmark results indicating a performance regression:

• Commit Run on ursa-i9-9960x at 2024-03-14 21:39:53Z

  • tpch (R) with engine=arrow, format=native, language=R, memory_map=False, query_id=TPCH-06, scale_factor=1

• Commit Run on test-mac-arm at 2024-03-15 18:48:32Z

  • tpch (R) with engine=arrow, format=parquet, language=R, memory_map=False, query_id=TPCH-06, scale_factor=1

The full Conbench report has more details. It also includes information about 2 possible false positives for unstable benchmarks that are known to sometimes produce them.