refactor(L1Reservoir): split _drip into smaller functions and rename some variables

[pcarranzav]

trafficstars

Split the _drip function into smaller pieces, hopefully making it cleaner and easier to understand.

We also rename mintedRewardsActual to lastDripRewardsUntilCurrentBlock, and mintedRewardsTotal to lastDripTotalRewards, hopefully making these closer to what they represent.

[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (pcv/l2-drip-rewards@559ea00). Click here to learn what that means. Patch has no changes to coverable lines.

Additional details and impacted files

@@                  Coverage Diff                   @@
##             pcv/l2-drip-rewards     #705   +/-   ##
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  Coverage                       ?   92.40%           
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  Files                          ?       45           
  Lines                          ?     2160           
  Branches                       ?      375           
======================================================
  Hits                           ?     1996           
  Misses                         ?      164           
  Partials                       ?        0           

Flag	Coverage Δ
unittests	92.40% <0.00%> (?)

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[pcarranzav]

CI failed because of https://github.com/graphprotocol/contracts/issues/576 - retrying

[pcarranzav]

Closing as GIP-0037 is believed to be the better alternative at this point (see https://forum.thegraph.com/t/gip-0037-the-graph-arbitrum-deployment-with-linear-rewards-minted-in-l2/3551)