refactor: make BloomFilterProperties fpp/ndv private with accessors

[CuteChuanChuan]

Which issue does this PR close?

• Follow-up to feat(parquet): add BloomFilterPropertiesBuilder #9877; completes the remaining scope of [parquet] Add BloomFilterProperties builder API to make bloom filter configuration explicit #9667 (making BloomFilterProperties fields non-public and exposing accessors).

Rationale for this change

#9877 introduced BloomFilterPropertiesBuilder. With the builder in place, the public fpp / ndv fields constrain future evolution. Locking them down behind accessors makes the public API smaller and more evolvable, matching the original direction outlined in #9667.

What changes are included in this PR?

• Make BloomFilterProperties::fpp and BloomFilterProperties::ndv private fields
• Add pub fn fpp(&self) -> f64 and pub fn ndv(&self) -> u64 accessor methods
• Move the per-field documentation verbatim onto the accessor methods so it remains rendered by rustdoc (private fields are not rendered)

Are these changes tested?

Yes — the existing test suite covers the affected paths

Are there any user-facing changes?

Yes — this is a breaking change to the public API.

• External struct-literal construction no longer compiles:

// Before — no longer works
BloomFilterProperties { fpp: 0.01, ndv: 10_000 }

// Use the builder added in #9877 instead:
BloomFilterProperties::builder()
  .with_fpp(0.01)
  .with_max_ndv(10_000)
  .build()

• Direct field reads (props.fpp, props.ndv) no longer compile; use props.fpp() / props.ndv() instead.

[adriangb]

Looks good to me! @alamb do we need to wait for some release before we merge this?

[etseidl]

Looks good to me. This is a breaking change, but luckily 'tis the season. 😄

[alamb]

Looks good to me. This is a breaking change, but luckily 'tis the season. 😄

🎄

[alamb]

Thank you @CuteChuanChuan @adriangb and @etseidl