Use protocol_dts_generator.ts from Chromium checkout

[Sergei-Rudenkov]

Generate types/ with Chromium's protocol_dts_generator.ts

Chromium has its own copy of this repo's .d.ts generator, at
//third_party/blink/public/devtools_protocol/scripts/protocol_dts_generator.ts,
which it uses in-tree to produce CDP TypeScript definitions for
inspector-protocol tests and for chromium-bidi. Two copies of the same
generator will drift apart.

Make Chromium the single source of truth and delete the copy here.
update-to-latest.sh already sparse-checks out
/third_party/blink/public/devtools_protocol/, so the generator arrives
with the .pdl files at no extra cost: no new fetch, no new dependency.

• Delete scripts/protocol-dts-generator.ts and scripts/protocol-schema.d.ts.
• Add scripts/build-protocol-dts.mjs, which locates the generator in the
  Chromium checkout and runs it. It exits with an actionable message rather
  than an ENOENT when the checkout is absent, and honours
  CHROMIUM_PROTOCOL_SCRIPTS_DIR so that anyone with a local Chromium
  checkout can regenerate types/ without running the full roll script.
• Generate the types in update-to-latest.sh directly after
  convert_protocol_to_json.py, rather than later inside the git diff block.
  A generator-only change in Chromium, with no .pdl change, therefore now
  produces a diff and rolls a release.
• Point the type-check in scripts/tsconfig.json at the published
  types/*.d.ts, since the generator it used to check no longer lives here.
• Document in README.md that the generator lives in Chromium and that
  changes to it belong there.

Regenerating with the Chromium script produces three differences in types/:
the Chromium copyright header, "import Protocol from './protocol.js'" in
place of "./protocol", and an additional "export type binary = string".
The specifier change was verified against a consumer importing
devtools-protocol, devtools-protocol/types/protocol-mapping.js and
devtools-protocol/types/protocol-proxy-api.js under moduleResolution
node10, node16 and bundler with skipLibCheck disabled; all three resolve
./protocol.js to protocol.d.ts. The remainder of types/ is byte-for-byte
unchanged.

[Sergei-Rudenkov]

@OrKoN could you please review?

This is the follow-up you suggested — the .d.ts generator now lives in Chromium, so this drops the duplicate copy here and reuses it. update-to-latest.sh already sparse-checks out third_party/blink/public/devtools_protocol/, so the generator comes along with the .pdl files at no extra cost.

cc @Lightning00Blade

[Lightning00Blade]

CC @paulirish, I was you had some changes ready to be merged here.

[Lightning00Blade]

Another thing that we can do is archive this repo and just publish from LUCI, like we plan to do with chromium-bidi.

[OrKoN]

Another thing that we can do is archive this repo and just publish from LUCI, like we plan to do with chromium-bidi.

This is not strictly necessary so we are not going to do it right now. Maybe later.

[OrKoN]

LGTM thanks. Please monitor GitHub Actions after landing this to make sure the releases still work.