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GH-15139: [C++] Improve bzip2 static library path detection for arrow.pc (#33712)

### Rationale for this change

If bzip2 is installed for debug build and release build on Windows, find_package(BZip2)
returns both static library paths of them. 

### What changes are included in this PR?

We should use one of detected library paths in arrow.pc.

The bzip2's official build system doesn't provide bzip2.pc but vcpkg provides bzip2.pc. We can use it instead of detecting bzip2's static library path by ourselves.

### Are these changes tested?

Yes. We test these changes in #15139 manually.

### Are there any user-facing changes?

No.
* Closes: #15139

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