refactor(tests): Introduce loading shims, use in playgrounds (#7380)

* refactor(build): Simplify implementation of posixPath

* fix(closure): Make safe to import in node.js

  Make the implementation declareModlueId safe to import and
  execute in node.js, which does not provide a window global.

  (N.B. because this is an ESM and therefore automatically
  strict, using window?.goog?.declareModuleId doesn't work
  because window being undefined is an early error.)

* feat(tests): Introduce chunk loading shims

  - Add a buildShims task to build_tasks.js that, for each chunk,
    creates a correspondingly-named build/<chunk>.mjs that will
    either (in uncompressed mode) import and reexport that chunk's
    entry point module (e.g. core/blockly.js) or (in compressed
    mode) load dist/<chunk>_compressed.js using a <script> tag
    and then export the corresponding properties on the chunk's
    exports object.

  - Provide helper methods used by these shims in
    tests/scripts/loading.mjs, including code to detect whether
    to load in compressed or uncompressed mode.

  - Add a quote() function to scripts/helpers.js, used by
    buildShims.  This is copied from tests/bootstrap_helper.js,
    which will be removed in a later commit.

* refactor(tests): Update playground.html to use new loading shims

* refactor(tests): Update advanced_playground.html to use new loading shims

* refactor(tests): Update multi_playground.html to use new loading shims

* chore(tests): Delete playgrounds/shared_procedures.html

  Shared procedure support was moved to a plugin and this should
  have been removed from core along with it.

* docs(tests): Typo corrections.

* chore(tests): Add ".loader" infix to shim filenames.

  Per suggestion on PR #7380, have buildShims name the shims
  ${chunk.name}.loader.mjs instead of just `${chunk.name}.mjs`.

scripts/helpers.js

@@ -11,25 +11,64 @@
 
 const path = require('path');
 
-/**
- * Escape regular expression pattern
- * @param {string} pattern regular expression pattern
- * @return {string} escaped regular expression pattern
- */
-function escapeRegex(pattern) {
-  return pattern.replace(/[-/\\^$*+?.()|[\]{}]/g, '\\$&');
-}
-
 /**
  * Replaces OS-specific path with POSIX style path.
+ * Simplified implementation based on
+ * https://stackoverflow.com/a/63251716/4969945
+ *
  * @param {string} target target path
  * @return {string} posix path
  */
 function posixPath(target) {
-  const osSpecificSep = new RegExp(escapeRegex(path.sep), 'g');
-  return target.replace(osSpecificSep, path.posix.sep);
+  return target.split(path.sep).join(path.posix.sep);
+}
+
+/**
+ * Convert a string into a string literal.  Strictly speaking we
+ * only need to escape backslash, \r, \n, \u2028 (line separator),
+ * \u2029 (paragraph separator) and whichever quote character we're
+ * using, but for simplicity we escape all the control characters.
+ *
+ * Based on https://github.com/google/CodeCity/blob/master/server/code.js
+ *
+ * @param {string} str The string to convert.
+ * @return {string} The value s as a eval-able string literal.
+ */
+function quote(str) {
+  /* eslint-disable no-control-regex, no-multi-spaces */
+  /** Regexp for characters to be escaped in a single-quoted string. */
+  const singleRE = /[\x00-\x1f\\\u2028\u2029']/g;
+
+  /** Map of control character replacements. */
+  const replacements = {
+    '\x00': '\\0',
+    '\x01': '\\x01',
+    '\x02': '\\x02',
+    '\x03': '\\x03',
+    '\x04': '\\x04',
+    '\x05': '\\x05',
+    '\x06': '\\x06',
+    '\x07': '\\x07',
+    '\x08': '\\b',
+    '\x09': '\\t',
+    '\x0a': '\\n',
+    '\x0b': '\\v',
+    '\x0c': '\\f',
+    '\x0d': '\\r',
+    '\x0e': '\\x0e',
+    '\x0f': '\\x0f',
+    '"': '\\"',
+    "'": "\\'",
+    '\\': '\\\\',
+    '\u2028': '\\u2028',
+    '\u2029': '\\u2029',
+  };
+  /* eslint-enable no-control-regex, no-multi-spaces */
+
+  return "'" + str.replace(singleRE, (c) => replacements[c]) + "'";
 }
 
 module.exports = {
   posixPath,
+  quote,
 };