Minor fixes for aero pool

[slundqui]

• Adding whale account in fork fuzzing.
• Fund as much as possible in the case where whale doesn't have enough balance.
• Call totalShares in get_vault_shares with fallback.
• Set vault_shares_token_contract to None if it's the zero address.
• get_variable_rate returns None if vault_shares_token_contract is None.

[codecov]

Codecov Report

Attention: Patch coverage is 32.00000% with 17 lines in your changes missing coverage. Please review.

Project coverage is 80.94%. Comparing base (a4665c5) to head (53ed8d0).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ent0/ethpy/hyperdrive/interface/_contract_calls.py	23.07%	10 Missing ⚠️
src/agent0/hyperfuzz/system_fuzz/run_fuzz_bots.py	50.00%	3 Missing ⚠️
...t0/core/hyperdrive/interactive/hyperdrive_agent.py	33.33%	2 Missing ⚠️
...gent0/ethpy/hyperdrive/interface/read_interface.py	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1725      +/-   ##
==========================================
+ Coverage   80.73%   80.94%   +0.21%     
==========================================
  Files          93       93              
  Lines        7029     7033       +4     
==========================================
+ Hits         5675     5693      +18     
+ Misses       1354     1340      -14     

Flag	Coverage Δ
unittests	80.94% <32.00%> (+0.21%)	⬆️

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