This is a continuation of #9726, which did not fix the problem
described.
If the initial network when the extension is started is something other
than Mainnet, the swaps controller will never successfully retrieve
swap quotes. This is because `ethers` will continue to communicate
with whichever network the provider was initially on.
We tried fixing this by hard-coding the `chainId` to Mainnet's
`chainId` when constructing the Ethers provider, but this did not work.
I suspect this failed because the `provider` we pass to `ethers` is not
compliant with EIP 1193, as `ethers` doubtless expects it to be.
Instead the entire `ethers` provider is now reconstructed each time the
network changes. This mirrors the approach we take in some other
controllers.
If the initial network when the extension is started is something other
than Mainnet, the swaps controller will never successfully retrieve
swap quotes. This is because the `ethers` provider used by the swaps
controller doesn't allow network changes by default - it assumes that
the network remains the same as when the provider was initialized.
This was fixed by hard-coding Mainnet as the initial chain ID for this
`ethers` provider used by the swaps controller.
Some adjustments needed to be made to the `provider` stub to allow
setting `1` as the network ID and chain ID in unit tests.
* Calculate savings per swap relative to median values
* Update test mock quotes, add getMedian tests
* Identify assets by sourceToken and destinationToken
* Stop passing a gas param to the estimateGas call initiated in the swaps controller timedoutGasReturn
* Stop passing gas params to timedoutGasReturn
* Lint fix
* Stop passing no longer used param to setInitialGasEstimate
The `_fetchAndSetSwapsLiveness` was accidentally passed to
`setInterval` without being bound first, so the `this` reference was
not defined when it was called. It is now bound before being passed to
`setInterval`.
