tests: switch to ganache v7

[ErikBjare]

WIP work on #200

[codecov]

Codecov Report

Merging #201 (2a5c791) into master (6e7529a) will increase coverage by 19.48%.
The diff coverage is 77.27%.

@@             Coverage Diff             @@
##           master     #201       +/-   ##
===========================================
+ Coverage   58.82%   78.31%   +19.48%     
===========================================
  Files          10       10               
  Lines         731      793       +62     
===========================================
+ Hits          430      621      +191     
+ Misses        301      172      -129     

Impacted Files	Coverage Δ
uniswap/uniswap.py	73.70% <77.27%> (+25.50%)	⬆️
uniswap/util.py	97.36% <0.00%> (+2.63%)	⬆️
uniswap/cli.py	92.42% <0.00%> (+3.03%)	⬆️

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