It fell out of date, so this commit updates the spec
to be more modern. It also removes the inlined solidity
interfaces for the contracts and instead adds a link
to the contract itself. This will help to prevent churn
with maintaining a copy of the interface inlined in
the spec. Some language is updated when describing each
predeploy. There is a tradeoff in having the contracts
themselves explain each function vs the spec explaining
each function.

feat(ctb): preserve legacy ETH invariant

ctb: Add echidna tests for Hashing

Preserves the invariant in LegacyERC20ETH that balanceOf(x) is always
the same as address(x).balance. balanceOf is the only function that was
not being blocked and contracts may exist that rely on this behavior.

fix(cmn): BaseServiceV2 options parsing bug

feat(cmn): make logLevel a default option

ctb: Add echidna tests for metering

maint(ctb): move default sender to constants

op-node: Preallocate slice

Updates BaseServiceV2 so that logLevel is a default option to any new
instantiation of BaseServiceV2. Avoids people having to include hacky
code to set the log level.

build(deps): bump express from 4.17.1 to 4.17.3

Moves the DEFAULT_L2_SENDER variable to Constants.sol since it's being
shared by both CrossDomainMessenger and OptimismPortal.

feat(ctb): add gas estimation logic to portal

Adds the same special gas estimation logic that we just added to the
CrossDomainMessenger into the OptimismPortal.

Fixes a bug in BaseServiceV2 where options would not be parsed correctly
when passed directly into the constructor rather than via the
environment or command line arguments.

fix: migration gaslimit

feat(ctb): update portal gas amount

Set the withdrawal migration gas limit to
a non zero number.

maint(ctb): comments for structs

Updates the amount of gas that can be sent to the target contract when
sending transactions through the Optimism portal. Previously, the amount
was specified as exactly the transaction gas limit. We now allow the
withdrawal to be sent with more than the transaction gas limit.

Adds comments for all structs in the current codebase, except the
SystemDictator which is going to be separately documented in the README
of contracts-bedrock.

maint(ctb): clean up getAdvancedContract

maint(ctb): add comment to structs in Types

Verify test names in CI

feat(ctb): type safety for deploy config

Cleans up the getAdvancedContract function and removes logic that was
originally meant only for use on Kovan which we don't deploy to anymore.

Adds new custom natspec to structs in the Types file. Undocumented
fields have created confusion in the past.

fix(ctb): Fix MerkleTrie test names to match convention