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GH-38984: [Python][Packaging] Verification of wheels on AlmaLinux 8 are failing due to missing pip (#38985)

### Rationale for this change

Almalinux 8 has been updated from 8.8 to 8.9. When using 8.9 python3 seems to be shipped without pip as  the command `python3 -m pip install -U pip` fails to find pip.

### What changes are included in this PR?

Use the [ensurepip package](https://docs.python.org/3/library/ensurepip.html) which provides support for bootstrapping the pip installer into an existing Python installation.

### Are these changes tested?

Yes via archery.

### Are there any user-facing changes?

No
* Closes: #38984

Authored-by: Raúl Cumplido <raulcumplido@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>