Refactor InListExpr into static-filter modules (apache#21649)

## Which issue does this PR close?

- Part of apache#19241.

## Rationale for this change

This PR is a preparatory refactor for
[apache#19390](apache#19390).

`InListExpr` currently mixes expression evaluation, constant-list filter
construction, primitive-vs-fallback dispatch, and generic fallback
execution in one file.

This PR extracts the existing static-filter code into smaller internal
modules while preserving the current behavior.

## Review guide

This PR is intended to be a move/extract-only refactor. The main review
question is whether the existing `InListExpr` static-filter behavior has
been preserved while making the internal structure easier to follow.

In particular:

- `in_list.rs` still owns `InListExpr` construction and evaluation
- `primitive_filter.rs` contains the existing primitive numeric
static-filter implementations moved out of `in_list.rs`
- `array_static_filter.rs` contains the existing `ArrayStaticFilter`
fallback moved out of `in_list.rs`
- `strategy.rs` contains the existing dispatch between primitive filters
and `ArrayStaticFilter`
- `static_filter.rs` defines the shared internal trait used by those
extracted pieces

No user-facing behavior or API changes are intended in this PR.

## Are these changes tested?

Yes. I validated this PR with:

- `cargo fmt --all`
- `cargo clippy -p datafusion-physical-expr --all-targets --all-features
-- -D warnings`
- `cargo test -p datafusion-physical-expr --all-features`

## Are there any user-facing changes?

No. This is an internal refactor only.

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

Author: geoffreyclaude