fix(performance): using RocksDBMempoolTipsIndex made the sync too slow

[jansegre]

Motivation

With the deploy of v0.62.0-rc.1 the sync from scratch took significantly longer than expected. The cause was confirmed to be the use of RocksDBMempoolTipsIndex that was introduced. The simplest solution to quickly advance with the release is to revert to MemoryMempoolTipsIndex.

Acceptance Criteria

• Revert back to MemoryMempoolTipsIndex for RocksDBIndexesManager.mempool_tips

Checklist

• [x] If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov[bot]]

Codecov Report

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

Project coverage is 84.85%. Comparing base (592f47c) to head (0a60ec7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## hotfix #1100 +/- ## ========================================== - Coverage 84.99% 84.85% -0.14% ========================================== Files 314 314 Lines 23957 23957 Branches 3621 3621 ========================================== - Hits 20362 20329 -33 - Misses 2880 2913 +33 Partials 715 715 ```

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