ref: delete unreachable upstream-fetcher modules

Stacked on the modifications PR. Now that no live code path references
the per-package fetchers, the shared HTTP/parsing helpers, the
in-process normalizer, or the example template, delete them. Pure
deletion — no behavior change.

- ~93 per-package <pkg>/releases.js fetcher modules.
- _common/{brew,fetcher,git-tag,gitea,github,github-source,
  githubish,githubish-source}.js shared HTTP/parsing helpers.
- _webi/normalize.js in-process normalization layer (cache files
  arrive normalized from webicached).
- _example/releases.js fetcher template for new packages.

The Go cache daemon (webicached) is now the sole producer of release
metadata; the Node process never makes an upstream request.

flutter/releases.js

@@ -1,132 +0,0 @@
-'use strict';
-
-let Fetcher = require('../_common/fetcher.js');
-
-let FLUTTER_OSES = ['macos', 'linux', 'windows'];
-
-/**
- * stable, beta, dev
- * @type {Object.<String, Boolean>}
- */
-let channelMap = {};
-
-// This can be spot-checked against
-// https://docs.flutter.dev/release/archive?tab=windows
-
-// The release URLs are
-// - https://storage.googleapis.com/flutter_infra_release/releases/releases_macos.json
-// - https://storage.googleapis.com/flutter_infra_release/releases/releases_linux.json
-// - https://storage.googleapis.com/flutter_infra_release/releases/releases_windows.json
-// The old release URLs are
-// - https://storage.googleapis.com/flutter_infra/releases/releases_macos.json
-// - https://storage.googleapis.com/flutter_infra/releases/releases_linux.json
-// - https://storage.googleapis.com/flutter_infra/releases/releases_windows.json
-
-// The data looks like
-// {
-//   "base_url": "https://storage.googleapis.com/flutter_infra/releases",
-//   "current_release": {
-//     "beta": "b22742018b3edf16c6cadd7b76d9db5e7f9064b5",
-//     "dev": "fa5883b78e566877613ad1ccb48dd92075cb5c23",
-//     "stable": "02c026b03cd31dd3f867e5faeb7e104cce174c5f"
-//   },
-//   "releases": [
-//     {
-//       "hash": "fa5883b78e566877613ad1ccb48dd92075cb5c23",
-//       "channel": "dev",
-//       "version": "2.3.0-16.0.pre",
-//       "release_date": "2021-05-27T23:58:47.683121Z",
-//       "archive": "dev/macos/flutter_macos_2.3.0-16.0.pre-dev.zip",
-//       "sha256": "f572b42d36714e6c58a3ed170b93bb414e2ced3ca4bde5094fbe18061cbcba6c"
-//     },
-//     {
-//       "hash": "02c026b03cd31dd3f867e5faeb7e104cce174c5f",
-//       "channel": "stable",
-//       "version": "2.2.1",
-//       "release_date": "2021-05-27T23:06:07.243882Z",
-//       "archive": "stable/macos/flutter_macos_2.2.1-stable.zip",
-//       "sha256": "6373d39ec563c337600baf42a42b258420208e4523d85479373e113d61d748df"
-//     },
-//     {
-//       "hash": "b22742018b3edf16c6cadd7b76d9db5e7f9064b5",
-//       "channel": "beta",
-//       "version": "2.2.0",
-//       "release_date": "2021-05-19T21:14:59.281482Z",
-//       "archive": "beta/macos/flutter_macos_2.2.0-beta.zip",
-//       "sha256": "31ab530e708f8d1274712211253a27a4ce7d676f139d30f2ec021df22382f052"
-//     }
-//   ]
-// }
-
-/**
- * @typedef BuildInfo
- * @prop {String} version
- * @prop {String} [_version]
- * @prop {Boolean} lts
- * @prop {String} channel
- * @prop {String} date
- * @prop {String} download
- * @prop {String} [_filename]
- */
-
-module.exports = async function () {
-  let all = {
-    download: '',
-    /** @type {Array<BuildInfo>} */
-    releases: [],
-    /** @type {Array<String>} */
-    channels: [],
-  };
-
-  for (let osname of FLUTTER_OSES) {
-    let resp;
-    try {
-      let url = `https://storage.googleapis.com/flutter_infra_release/releases/releases_${osname}.json`;
-      resp = await Fetcher.fetch(url, {
-        headers: { Accept: 'application/json' },
-      });
-    } catch (e) {
-      /** @type {Error & { code: string, response: { status: number, body: string } }} */ //@ts-expect-error
-      let err = e;
-      if (err.code === 'E_FETCH_RELEASES') {
-        err.message = `failed to fetch 'flutter' release data for ${osname}: ${err.response.status} ${err.response.body}`;
-      }
-      throw e;
-    }
-    let data = JSON.parse(resp.body);
-
-    let osBaseUrl = data.base_url;
-    let osReleases = data.releases;
-
-    for (let asset of osReleases) {
-      if (!channelMap[asset.channel]) {
-        channelMap[asset.channel] = true;
-      }
-
-      all.releases.push({
-        version: asset.version,
-        _version: `${asset.version}-${asset.channel}`,
-        lts: false,
-        channel: asset.channel,
-        date: asset.release_date.replace(/T.*/, ''),
-        download: `${osBaseUrl}/${asset.archive}`,
-        _filename: asset.archive,
-      });
-    }
-  }
-
-  all.channels = Object.keys(channelMap);
-
-  // note: versions have a waterfall relationship with channels:
-  // - a release that is in beta today may become stable tomorrow
-  // - semver prereleases are either beta or dev
-
-  return all;
-};
-
-if (module === require.main) {
-  module.exports().then(function (all) {
-    all.releases = all.releases.slice(25);
-    console.info(JSON.stringify(all, null, 2));
-  });
-}