Remove supports1559

[nambrot]

celo-org/optics-monorepo@7954faf on the optics-monorepo added the supports1559 logic that explicitly sets the transaction type. Because of it, we have been mistakenly assuming that to have type 2 transactions, the transaction config has to manually specify the fields in the overrides. It turns out that

1. ethers.rs supports 1559 automatically by detecting support via the RPC
2. We actually haven't been setting the tx type anyways due to the recent SDK refactor where fixOverrides is only used in getMultiProviderFromConfigAndSigner which is only used in the test environment.

Thus this PR removes that special casing. It also treats the sdk's IChainConnectionConfig as sufficient for infra's TransactionConfigs. In a future PR, those types should probably be merged

This PR also removes ChainConnections mutative functions as they are currently unused. The original intention is to be able to change ChainConnection fields at runtime. It's unclear to me when that really would be useful, with the possible exception of changing the signer. However, the abstraction change that we underwent with the SDK overhaul doesn't account for state changes in ChainConnection/MultiProvider anyways, so we'll have to think about it from sctrach

Fixes #366

[tkporter]

I have a feeling Yorke has more context on the other changes (like the change to getMultiProviderFromConfigAndSigner and the code removal)