[VOTE] Add ListElement document granularity to FTS indexes

[Xuanwo]

This vote proposes accepting the FTS format changes in PR #7788. It adds ROW and LIST_ELEMENT document granularities to inverted-index metadata. ROW remains the default for existing metadata; LIST_ELEMENT treats each element of the deepest list on the field path as a document and persists its root-to-leaf coordinates. Element-document indexes use index version 4, while existing row-document indexes remain unchanged.

PR: #7788

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