MCP23XXX Refactor

[jesserockz]

Description:

This refactors the MCP23008, MCP23017, MCP23S08 and MCP23S17 to remove duplicate code and inherit from new base classes.

It also removes the duplicate pin schemas and consolidates all 4 into a single new schema with key mcp23xxx for the component id.

Related issue (if applicable): fixes

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#1028

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @SenexCrenshaw, mind taking a look at this pull request as its been labeled with an integration (mcp23S17) you are listed as a codeowner for? Thanks!
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[kbx81]

@jesserockz this is looking good! I want to test it out but time keeps getting away from me. I rolled through the code, though, and I like how you've (re)arranged things. 😄

[glmnet]

This pr has lots of changes with files with almost the same name and reviewing file changes with just formattings is quite annoying waste of time. I've seen other people already do this and asked him to rollback the format change, I'm ok with a formatter update on the codebase but that will be another PR

[jesserockz]

This pr has lots of changes with files with almost the same name and reviewing file changes with just formattings is quite annoying waste of time. I've seen other people already do this and asked him to rollback the format change, I'm ok with a formatter update on the codebase but that will be another PR

Yeah sorry, I just ran black mcp*

[probot-esphome]

Hey there @SenexCrenshaw, mind taking a look at this pull request as its been labeled with an integration (mcp23S17) you are listed as a codeowner for? Thanks!
_{^{(message by CodeOwnersMention)}}