[Mobile Payments] Duplicate CardReaderConnectionController for built in reader flow

[joshheald]

Part of: #8082

Description

Apologies for the length: this PR duplicates an existing file.

The connection flows for BuiltIn and Bluetooth card readers are different, but similar. As a first step towards modelling this, I've duplicated the CardReaderConnectionController in order to make a BuiltIn variant.

Once both variants are working, I'll factor out the shared code.

No rush on these: I've put them into next week's milestone

Testing instructions

Check you can still take a payment using a bluetooth reader (with the feature flag off)
Run unit tests

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

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• Then installing the build number pr8280-bec3cb5 on your iPhone

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[toupper]

This class looks massive, probably because of the enums and comments inside, but I think it's doing many things in one place. Did you consider splitting it into several other classes/files to make it easier to maintain and work with?

[joshheald]

Agreed. It's a duplicate of the existing massive CardReaderConnectionController, and my immediate plan is to share the common code between them. This should help with the size, and once that's done I think it'll be worth addressing whether it's doing too much.

In general, it's covering a well-scoped responsibility (connecting to a reader), but perhaps the software updates could be moved out of here, or the error handling.

Another approach (which would be a separate project really) would be to turn it all the way in to a state machine. It looks like it's built with that in mind, but it doesn't have the core of the state machine which decides how to handle transitions from x state based on y input, the transitions are all individually coded.

[toupper]

The code looks great (thanks a lot for all the comments) and it tests well. I just added a small suggestion there.