[VOTE] Add SparseLayout to Lance 2.3

[Xuanwo]

This vote proposes accepting the Lance 2.3 SparseLayout wire contract. It represents sparse nested structure with semantic position/count sets, supports both null-position and valid-position validity encodings, and stores only visible leaf values while preserving Arrow null/empty semantics. It is gated to Lance 2.3 and does not change Lance 2.2.

Proposal: #7631
PR: #7754

Per the Lance voting process, this requires 3 binding +1 votes from PMC members, excluding the proposer, and a minimum voting period of one week. Please vote +1, 0, or -1 and mark the vote binding or non-binding; -1 votes must include justification.