sparse float vector index to support mmap when loading from index file

[zhengbuqian]

issue: https://github.com/milvus-io/milvus/issues/29419

/kind: improvement

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zhengbuqian

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 71.69%. Comparing base (3c46f4c) to head (8f6c703). Report is 24 commits behind head on main.

Additional details and impacted files

[](https://app.codecov.io/gh/zilliztech/knowhere/pull/530?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zilliztech) ```diff @@ Coverage Diff @@ ## main #530 +/- ## ========================================= + Coverage 0 71.69% +71.69% ========================================= Files 0 67 +67 Lines 0 4431 +4431 ========================================= + Hits 0 3177 +3177 - Misses 0 1254 +1254 ``` [see 67 files with indirect coverage changes](https://app.codecov.io/gh/zilliztech/knowhere/pull/530/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zilliztech)

[alexanderguzhva]

/lgtm