Reapply UltraGreen changes (send fee to FeeHandler)

[karlb]

These changes have been temporarily reverted in https://github.com/celo-org/celo-blockchain/commit/2bced8bed6b111e516557b81fb8b50a5680970bf to make it easier to merge https://github.com/celo-org/celo-blockchain/pull/2102.

Now that this is done, we can reapply these changes.

The only merge conflicts were in https://github.com/celo-org/celo-blockchain/pull/2146/commits/4d2b28768cb5091ba65f68c564c91ed187bf888d, so it should be sufficient to review that commit again.

[github-actions[bot]]

Coverage from tests in ./e2e_test/... for ./consensus/istanbul/... at commit cd5458204f54d521d7150a157e56a2668c0c4f17

coverage: 50.0% of statements across all listed packages

coverage:  60.2% of statements in consensus/istanbul
coverage:  43.1% of statements in consensus/istanbul/announce
coverage:  55.7% of statements in consensus/istanbul/backend
coverage:   0.0% of statements in consensus/istanbul/backend/backendtest
coverage:  24.3% of statements in consensus/istanbul/backend/internal/replica
coverage:  63.2% of statements in consensus/istanbul/core
coverage:  50.0% of statements in consensus/istanbul/db
coverage:   0.0% of statements in consensus/istanbul/proxy
coverage:  64.4% of statements in consensus/istanbul/uptime
coverage:  51.8% of statements in consensus/istanbul/validator
coverage:  79.2% of statements in consensus/istanbul/validator/random

[github-actions[bot]]

Test failures:
TestSyncNoStorageAndOneCodeCappedPeer: snap sync_test.go:1105: Error, expected < 100 invocations, got 111
This test report was produced by the test-summary action.  Made with ❤️ in Cambridge.

[codecov[bot]]

Codecov Report

Patch coverage: 85.71% and project coverage change: -0.06 :warning:

Comparison is base (e10394d) 55.31% compared to head (a0b56f0) 55.25%.

:exclamation: Current head a0b56f0 differs from pull request most recent head fe80e8c. Consider uploading reports for the commit fe80e8c to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2146 +/- ## ========================================== - Coverage 55.31% 55.25% -0.06% ========================================== Files 675 675 Lines 113723 113729 +6 ========================================== - Hits 62905 62846 -59 - Misses 46974 47027 +53 - Partials 3844 3856 +12 ``` | [Impacted Files](https://app.codecov.io/gh/celo-org/celo-blockchain/pull/2146?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=celo-org) | Coverage Δ | | |---|---|---| | [mycelo/env/core\_contracts.go](https://app.codecov.io/gh/celo-org/celo-blockchain/pull/2146?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=celo-org#diff-bXljZWxvL2Vudi9jb3JlX2NvbnRyYWN0cy5nbw==) | `0.00% <ø> (ø)` | | | [core/state\_transition.go](https://app.codecov.io/gh/celo-org/celo-blockchain/pull/2146?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=celo-org#diff-Y29yZS9zdGF0ZV90cmFuc2l0aW9uLmdv) | `68.37% <85.71%> (+0.52%)` | :arrow_up: | ... and [25 files with indirect coverage changes](https://app.codecov.io/gh/celo-org/celo-blockchain/pull/2146/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=celo-org)

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