chore: Remove redundant OP stack implementations

[pxrl]

These are now handled via the OP_Adapter and OP_SpokePool implementations.

[pxrl]

This needs to be restored because the OP_SpokePool does not support Circle Bridged USDC.

[pxrl]

Restore this (per above).

[pxrl]

Just to add some more commentary around the conclusion that these contracts can be removed:

• There are three basic variations of OP contracts we can support:
  • USDC is an ERC20 bridged token.
  • USDC is an instance of Circle Bridged (Upgradable) USDC.
  • USDC is an instance of Circle Native USDC (...and optionally, bridged USDC is an ERC20 bridged token).

The current supported chains are:
[1,10,137,288,42161,324,8453,59144,34443,1135,81457,534352,690,7777777,480,41455,57073,1868,130,232,56,34268394551451,999,9745,143,4326]

Of this, the following are some variant of OVM/OP stack:

• 10, 288, 8453, 34443, 1135, 81457, 690, 7777777, 480, 57073, 1868, 130, 4326.

Blast (81457) is a snowflake, where USDC isn't even supported.

These chains are no longer supported by Across:

• 288, 690

These chains are Native USDC + optional ERC20 bridged USDC:

• 10, 8453, 480, , 57073, 130

These chains are ERC20 bridged USDC:

• 34443, 7777777

These chains are Circle Bridged (Upgradable) USDC:

• 1135, 1868

The latter category are not supported by the OP_SpokePool because it doesn't implement support for Circle Bridged USDC. For these two chains we therefore need to retain custom contract instances.

For the Native USDC or ERC20 bridged USDC chains, the OP_SpokePool will work fine.

cc @bmzig