GH-37065: [C++][Parquet] use std::optional in parquet statistics

[Alvaro-Kothe]

Rationale for this change

Simplify parquet statistics handling by using std::optional instead of has_xxx boolean + xxx attribute.

What changes are included in this PR?

• Remove has_xxx public attributes for parquet statistics in favor of using std::optional
• Deprecate some methods to construct the statistics (don't know if it was necessary)
• Add new methods to handle std::optional

Are these changes tested?

Partially. The new changes are tested by the existing C++ test-suite. The deprecated methods aren't being tested.

Are there any user-facing changes?

Yes.

This PR includes breaking changes to public APIs.

This PR:

• removes and modifies attributes in EncodedStatistics class;
• deprecate methods that use signatures containing arguments with xxx + has_xxx.

• GitHub Issue: [C++][Parquet] Provide std::optional-based APIs for statistics #37065

[Alvaro-Kothe]

Most of the CI errors are due to compiler warnings in c_glib due to the deprecations in statistics.h. Before diving deeper into fixing them, I'd like to ask for guidance on three points:

1. Should I proceed with the deprecation of these methods, should I remove them directly, or is there a better way to handle this migration?
2. I removed several public attributes and changed the type to some of them. Should I re-add these as deprecated members to maintain backward compatibility, or is the migration to std::optional sufficient?
3. The Statistics class in parquest_types.h also uses a similar mechanism of boolean flags to keep track of what is defined. Should I also migrate it to use std::optional?

cc: @pitrou @felipecrv