## Issue being fixed or feature implemented
When DKG data recovery is triggered by `qgetdata` the data we use to
construct `qdata` reply is actually the one handled by
`CDKGSessionManager`, not by `CQuorumManager`. Not storing the data long
enough in `CDKGSessionManager` will result in this data simply not being
recoverable.
Also, the formula in `CDKGSessionManager::CleanupOldContributions()` is
broken for quorums which use rotation (the depth is way too large).
## What was done?
Fix both issues by redefining `keepOldKeys` and aligning key storage
depths in both modules.
## How Has This Been Tested?
## Breaking Changes
n/a
## Checklist:
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [ ] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_
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