feat: update pre_mine specification (#6606)

Description
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Updated the pre_mine specification to cater for more releases.

Motivation and Context
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See above.

How Has This Been Tested?
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Added a new unit test `fn test_contributors_upfront_release_totals()`.

What process can a PR reviewer use to test or verify this change?
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Code review.

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Breaking Changes
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- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

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