(feat) Add support for extension config schemas

[brandones]

Requirements

• This PR has a title that briefly describes the work done, including the ticket number if there is a ticket.

For changes to apps

• My work conforms to the OpenMRS 3.0 Styleguide.

If applicable

• My work includes tests or is validated by existing tests.
• I have updated the esm-framework mock to reflect any API changes I have made.

Summary

Currently, extensions inherit the configuration schemas of the modules in which they are defined. Some extensions (especially generic ones) have highly specific configuration requirements, which pollute the module config schema: see here in patient-chart.

This makes it so that extensions can have their own schema, apart from the module schema.

Unrelatedly, this removes some dead code. It is not used anywhere.

[github-actions]

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Error: Error while trying to collect info after merging config-extension-schema into master.

Error: Command failed: git fetch --no-tags --prune origin config-extension-schema
fatal: couldn't find remote ref config-extension-schema

    at ChildProcess.exithandler (node:child_process:397:12)
    at ChildProcess.emit (node:events:394:28)
    at maybeClose (node:internal/child_process:1067:16)
    at Socket. (node:internal/child_process:453:11)
    at Socket.emit (node:events:394:28)
    at Pipe. (node:net:672:12)

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_{Generated by @jsenv/file-size-impact during Report bundle size#2000498149 on bbdc9b5}

[ibacher]

LGTM! I really like this feature!