refactor(index): add base offset to InvertedIndexMeta (#124)

* feat: add base offset to `InvertedIndexMeta`

Signed-off-by: Zhenchi <zhongzc_arch@outlook.com>

* chore: rename fields to reduce confused

Signed-off-by: Zhenchi <zhongzc_arch@outlook.com>

* fix: make

Signed-off-by: Zhenchi <zhongzc_arch@outlook.com>

* Update proto/greptime/v1/index/inverted_index.proto

Co-authored-by: Ruihang Xia <waynestxia@gmail.com>

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Signed-off-by: Zhenchi <zhongzc_arch@outlook.com>
Co-authored-by: Ruihang Xia <waynestxia@gmail.com>