test(openapi-generator): replace ava with node:test

This commit replaces ava with the Node.js native test runner[^1].

The naive implementation ran each test in the test corpus serially, due
to this nature of the native test runner's execution model[^2]:

> Each test file is executed as if it was a regular script. That is,
> if the test file itself uses node:test to define tests, all of those
> tests will be executed within a single application thread, regardless
> of the value of the concurrency option of test().

Since the function under test is synchronous and compute-bound, and
Node.js is single-threaded, all the tests were executing serially and
took over 30s to complete on my macbook.

Consequently, this commit uses Node.js worker threads[^3] to spawn one
worker per test-corpus file, limited to one worker per CPU core. In this
configuration, all tests complete in 17s on my macbook.

[^1]: https://nodejs.org/api/test.html
[^2]: https://nodejs.org/api/test.html#test-runner-execution-model
[^3]: https://nodejs.org/api/worker_threads.html

Author: ericcrosson-bitgo

.github/workflows/ci.yml

@@ -14,7 +14,15 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [lts/-2, lts/-1, lts/*]
+        node-version:
+          # Skip lts/-2 while it refers to Node.js 14, since this version
+          # does not come with Node.js's built-in test runner.
+          # - lts/-2
+          # Skip lts/-1 while it refers to Node.js 16, since this version
+          # ships with a segfault when collecting code coverage with
+          # Node.js's built-in test runner.
+          # - lts/-1
+          - lts/*
 
     name: Node.js ${{ matrix.node-version }}
     steps:
@@ -27,11 +35,6 @@ jobs:
           cache: npm
           node-version: ${{ matrix.node-version }}
 
-      # Install npm greater-than-or-equal-to 7 so we can use npm workspaces.
-      # We can remove this when Node.js 16 is the oldest LTS
-      - name: Update npm
-        run: npm install --global 'npm@>7'
-
       - name: Install dependencies
         run: npm ci