more readable _node urls (and cache structure)

[Fil]

Since we're free to name the resolutions of /_node/ files (bare module specifiers) as we want, why not give them names that are easy to read in the browser's network tab and make cache busting easier.

Here's what this combination gives when using node_modules versions of duckdb-wasm, d3-array and internmap@1 (when d3-array requires internmap@2, generating two files):

<link rel="modulepreload" href="./_node/internmap@1.0.1/77f92c63/internmap.js">
<link rel="modulepreload" href="./_node/d3-array@3.2.4/a6083063/d3-array.js">
<link rel="modulepreload" href="./_node/@duckdb/duckdb-wasm@1.28.1-dev106.0/5e9b2fc6/duckdb-wasm.js">
<link rel="modulepreload" href="./_node/internmap@2.0.3/e0fb710d/internmap.js">
<link rel="modulepreload" href="./_node/apache-arrow@14.0.2/8d522eb1/apache-arrow.js">
<link rel="modulepreload" href="./_node/tslib@2.6.2/b26fe5c0/tslib.js">
<link rel="modulepreload" href="./_node/flatbuffers@23.5.26/ada4f5af/flatbuffers.js">


...

const duckdb = await import("./_node/@duckdb/duckdb-wasm@1.28.1-dev106.0/5e9b2fc6/duckdb-wasm.js");
const MANUAL_BUNDLES = {
  mvp: {
    mainModule: new URL("./_node/@duckdb/duckdb-wasm@1.28.1-dev106.0/b08f36ee/duckdb-mvp.wasm", location).href,
    mainWorker: new URL("./_node/@duckdb/duckdb-wasm@1.28.1-dev106.0/b6de1549/duckdb-browser-mvp.worker.js", location).href
  },
  eh: {
    mainModule: new URL("./_node/@duckdb/duckdb-wasm@1.28.1-dev106.0/75338043/duckdb-eh.wasm", location).href,
    mainWorker: new URL("./_node/@duckdb/duckdb-wasm@1.28.1-dev106.0/d80d9fe7/duckdb-browser-eh.worker.js", location).href
  },
};

This also removes the extractNodeSpecifier function which was has no more purpose.

(Leaving as a draft for now because it might depend on whether we are doing the same for /_npm/, see #1165 (comment).)

[mbostock]

This seems like purely an aesthetic choice, so I’m not as motivated to change this as I am in #1165 which is fixing a preview server crash and broken imports (e.g., npm:mime/lite). We can already consider everything in _node (and _npm) immutable even though it doesn’t have an explicit content hash in the path because the published contents of npm packages should never change. And you can change the devtools to show the path rather than the file name to avoid seeing _esm.js. That’s not to say this PR isn’t an improvement, perhaps; it’s just I’m going to prioritize working on the other changes. 🙏