Allow configuring default sender account in Buidler plugin

[frangio]

The default sender account is hardcoded to accounts[0]. I'd like to be able to configure it to something else.

solidity-coverage/plugins/buidler.plugin.js

Line 66 in f1d4001

network.from = accounts[0];

[cgewecke]

@frangio

This should be fixed in the Hardhat plugin now. Whatever you specify as from in your Hardhat (or other) network config should persist when coverage runs the tests as well.

0.7.12