Fix REST API urls in documentation

[lhotari]

Fixes apache/pulsar#21573

All REST API urls are incorrect in the documentation. This PR fixes the URLs for next, 4.0.x and 3.0.x.

This PR adds a custom Remark plugin that handles logic to lookup the correct URL from the Swagger JSON file so that it's always correct. The plugin is written in Typescript and to do that, the docusaurus config was converted to .ts extension and made compatible.

There's a remaining problem that the Swagger files contain a lot of duplicate operations even after apache/pulsar#19193. The links to Swagger documentation won't work when there are duplicates, which is very common. A replacement will be needed in apache/pulsar for the Swagger generation to fix it. The duplicate operation names required adding ways to find the correct operation in the custom Remark plugin.

This PR replaces the previous draft PR #866.

[lhotari]

some remaining work to fix the issue at

pulsar-site/src/utils/index.js

Line 8 in 8df3779

import siteConfig from '../../docusaurus.config';

. I'll fix that.