Remove AlertPatcher

[hannesj]

There are some todos left in the SIRI-SX updater, as well as tests.

To be completed by pull request submitter:

• issue: Fixes Remove AlertPatcher #3114
• roadmap: Check the roadmap for this feature or bug. If it is not already on the roadmap, PLC will discuss as part of the review process.
• tests: Have you added relevant test coverage? Are all the tests passing on the continuous integration service (Travis CI)?
• formatting: Have you followed the suggested code style?
• documentation: If you are adding a new configuration option, have you added an explanation to the configuration documentation tables and sections?
• changelog: add a bullet point to the changelog file with description and link to the linked issue

To be completed by @opentripplanner/plc:

• reviews and approvals by 2 members, ideally from different organizations
• after merging: update the relevant card on the roadmap

[t2gran]

I general I think this looks good, and I am in favor of merging this and then fix any problems if any. @gmellemstrand or @lassetyr could make the approval after coordinating on reviewing the Siri updaters and testing it. At Entur we should patch the Transmodel API as soon as possible after the merge, since this is blocking us from merging it into our OTP2 production branch.

[t2gran]

@lassetyr Would you mind to review this part? The changes to the Siri updaters.

[lassetyr]

Looks good, I am also in favor of merging.

[abyrd]

I agree with @t2gran, this looks good, we can merge and update later if we spot any problems. @lassetyr has confirmed he doesn't expect any conflicts if we merge this first, then he merges the result into the siri branch.

Fixed all issues