refactor(Ethereum): improve efficiency of SafeProxy detection heuristic

[fubuloubu]

What I did

Narrow the heuristic which triggers the masterCopy() call to a contract to determine if it is a SafeProxy type. This should reduce/eliminate most of the instances where Ape tries the call and it fails and creates a log like so:

reverted without message
0xC8C8...6793.0xa619486e()

How I did it

We can add a couple extra ~free checks on code and slot_0 value before triggering masterCopy():

1. check that the method ID for masterCopy() (0xa619486e) is actually in the proxy code (should always be true, but has potential for false positives)
2. check that slot_0 is "address-like" (has 12 leading empty bytes, and at least 12/32 non-empty bytes)

How to verify it

Anything weird happens

Checklist

• All changes are completed
• Change is covered in tests
  - [ ] Documentation is complete

[fubuloubu]

With:

$ rm ~/.ape/optimism/mainnet/**/0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507.json
$ ape console --network optimism:mainnet:node
INFO:     Connecting to existing Reth node at https://optimism-rpc.publicnode.com.
                                                                      
In [1]: Contract("0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507")
Out[1]: <UniversalRouter 0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507>

Without:

$ rm ~/.ape/optimism/mainnet/**/0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507.json
$ ape console --network optimism:mainnet:node
INFO:     Connecting to existing Geth node at https://mainnet.optimism.io.

In [1]: Contract("0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507")
0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507.0xa619486e()
Out[1]: <UniversalRouter 0x851116D9223fabED8E56C0E6b8Ad0c31d98B3507>