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GH-43467: [C++] Add support for the official LZ4 CMake package (#43468)

### Rationale for this change

LZ4 1.10.0 provides `LZ4::lz4` but LZ4 1.9.4 provides only `LZ4::lz4_shared` and `LZ4::lz4_static`. So we need to prepare `LZ4::lz4` in our side.

### What changes are included in this PR?

Define `LZ4::lz4` by `LZ4::lz4_shared` or `LZ4::lz4_static` if `LZ4::lz4` doesn't exist.

### Are these changes tested?

Yes.

### Are there any user-facing changes?

Yes.
* GitHub Issue: #43467

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Jacob Wujciak-Jens <jacob@wujciak.de>