Update docs and comments to refer to scip-typescript

Created by: varungandhi-src

Fixes https://github.com/sourcegraph/sourcegraph/pull/34097

I've broken down the changes for commit-by-commit review:

• I've deleted the old tutorial, because I think it is superseded by the newer documentation on running lsif-typescript locally.
• Most references to lsif-tsc have been updated to `lsif-typescript. There's one reference which I wasn't sure if it needs updating:

  // canonicalizeDocuments determines if multiple documents are defined with the same URI. This can
  // happen in some indexers (such as lsif-tsc) that index dependent projects into the same index

  Does this point apply to lsif-typescript too? I haven't checked...
  • Strictly speaking a bunch of tests didn't need updating. I can remove those changes if desired.
• I've rewritten the how-to guide. Since almost all the examples are removed, I will re-add examples as a subsequent task, once we've ported over more of the "showcase" repositories.

Test plan

Setup CI to use the different documented setups.