Add source map for every possible element in the Markdown preview

[Lemmingh]

This PR fixes #133376

Summary

We have to clean up type definitions before the main work.

• Update markdown-it and type definitions

  • Update markdown-it and its DT so that they match now.
  • Update dompurify and its DT so that they match now.
  • Remove @types/highlight.js because highlight.js has its own type definitions since version 10.
  • Fix mismatches related to markdown-it. Note that lots of any are removed to allow TypeScript to infer type.

• Refresh the source map mechanism in markdownEngine.ts

  • Replace addLineNumberRenderer() with pluginSourceMap as described in Add source map for every block-level element in the Markdown preview #133376.

Note on attrSet() and attrGet()

markdown-it's Token is designed in a bad smell with no access control.

Given Renderer.renderAttrs() and the HTML Standard, an attribute set via Token.attrSet() should still work even in extreme cases.

The use of Token.attrGet() is for a similar reason.

[mjbvz]

LGTM! The new logic seem good and thanks for the additional cleanup!

[mjbvz]

Will be in the next insiders build and schedule to ship in stable as part of VS Code 1.62