Allow initial deposits to activate validators

[naddison36]

Changes

While the Ethereum validator deposit queue is long (> 20 days), doing two deposits to get an active validator is too long. This change allows the governor to set the initial deposit to 32.25 ETH which will allow a validator to become active from just one deposit.
Once the deposit queue gets down to a more reasonable length, eg < 10 days, the initial deposit can be changed back to 1 ETH via a governance proposal.

Code Change Checklist

To be completed before internal review begins:

• The contract code is complete
• Executable deployment file
• Fork tests that test after the deployment file runs
• Unit tests *if needed
• The owner has done a full checklist review of the code + tests

Internal review:

• Two approvals by internal reviewers

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.94%. Comparing base (78e4669) to head (630f246).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2885      +/-   ##
==========================================
+ Coverage   41.59%   41.94%   +0.35%     
==========================================
  Files         113      113              
  Lines        4916     4925       +9     
  Branches     1362     1365       +3     
==========================================
+ Hits         2045     2066      +21     
+ Misses       2868     2856      -12     
  Partials        3        3              

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[sparrowDom]

Looks good. There is one thing in the tests where comments don't align with code. Also I think it would be cool, that both compounding staking strategy contract setups are tested: when initial deposit is configured to 1 ETH / 32.24 ETH.

[sparrowDom]

Multiple places in the test files comments state that 32.25 ETH has been deposited while using a constant INITIAL_DEPOSIT_AMOUNT which is set to 1 ETH.