refactor(physical-expr): add proto ctx expr helpers and adopt in InList/Like

[adriangb]

Which issue does this PR close?

• Part of [EPIC] Port PhysicalExpr implementations to use try_from_proto / try_to_proto #22418 (decentralizing datafusion-proto serialization onto the expressions themselves; follows Split proto serialization to encapsulate private state #21835, Port LikeExpr to use try_to_proto / try_from_proto #22471, refactor: port InListExpr to use try_to_proto/try_from_proto hooks #22503).

Rationale for this change

Expressions migrating to the try_to_proto / try_from_proto hooks keep hand-rolling the same boilerplate that the central datafusion-proto match already factors out via parse_physical_exprs, parse_required_physical_expr, and serialize_physical_exprs. Those free functions can't be reused by expression authors: they take PhysicalProtoConverterExtension / PhysicalPlanDecodeContext, which the PhysicalExprEncodeCtx / PhysicalExprDecodeCtx surfaces deliberately hide.

This was raised in review on #22503 — rather than re-implement the list maps and "missing required field" checks in every migrated expression, expose the same shapes on the ctx structs.

What changes are included in this PR?

• datafusion-physical-expr-common: three thin convenience methods, built on the existing encode_child / decode primitives:
  • PhysicalExprEncodeCtx::encode_children_expressions
  • PhysicalExprDecodeCtx::decode_required_expression (also standardizes the Missing required field "<name>" error so each expression no longer spells its own)
  • PhysicalExprDecodeCtx::decode_children_expressions
• datafusion-physical-expr: adopt them in InListExpr and LikeExpr, removing the hand-rolled list maps and per-field ok_or_else checks.

Behavior note

decode_required_expression couples the presence check with the decode, so LikeExpr now decodes children left-to-right rather than validating both required fields up front. The end result is unchanged (a missing required field still errors), but a present sibling is decoded before a later missing field is reported. The try_from_proto_rejects_missing_pattern unit test is updated to reflect this.

Are these changes tested?

Yes — covered by existing tests, no new ones needed:

• The isolated proto_tests modules in in_list.rs and like.rs already exercise all three helpers (list encode/decode, required decode, and the missing-field + child-error paths) through the migrated try_to_proto / try_from_proto.
• The datafusion-proto round-trip integration tests (roundtrip_inlist, roundtrip_like, roundtrip_filter_with_not_and_in_list, test_tpch_part_in_list_query_with_real_parquet_data, etc.) continue to pass.
• cargo clippy --all-targets --features proto -D warnings is clean on the touched crates; cargo fmt --all applied.

Are there any user-facing changes?

No. The per-expression missing required field error wording is preserved: LikeExpr is byte-for-byte identical, and InList only changes its label from InList to InListExpr (the actual type name). The format now lives in one place (decode_required_expression) instead of being hand-spelled per expression.

[adriangb]

@kumarUjjawal since you've reviewed some of the PRs for this EPIC could you take a look at this PR?

[Copilot]

Pull request overview

This PR adds small proto encode/decode helper methods to PhysicalExprEncodeCtx / PhysicalExprDecodeCtx (in datafusion-physical-expr-common) and adopts them in LikeExpr and InListExpr to remove repeated boilerplate when implementing try_to_proto / try_from_proto for physical expressions.

Changes:

• Added encode_children_expressions to PhysicalExprEncodeCtx for encoding repeated child expression fields.
• Added decode_required_expression (standardized missing-required-field error) and decode_children_expressions to PhysicalExprDecodeCtx.
• Refactored LikeExpr and InListExpr proto encode/decode implementations + adjusted the affected unit tests accordingly.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
datafusion/physical-expr-common/src/physical_expr.rs	Adds encode/decode convenience helpers on the proto ctx types to centralize repeated patterns.
datafusion/physical-expr/src/expressions/like.rs	Uses decode_required_expression for required children; updates test to reflect decode-before-missing-field behavior.
datafusion/physical-expr/src/expressions/in_list.rs	Uses decode_required_expression / decode_children_expressions / encode_children_expressions; updates missing-field test expectation.

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[kumarUjjawal]

Thanks @adriangb Looks good!