Support node v18 and hapi v21, drop node v12 and hapi v19

[devinivy]

• Test on node v14+ and hapi v20+.
• Update to node v18-compatible versions of hapi modules, update lru-cache.
• Ensure all exports are available when used as ESM module.

If this looks good, this will go out as inert v7.

This PR may be used as an example of a plugin update for node v18 and hapi v21. Here's the checklist:

• Update the license for the current year.
• Update the workflow file to test on node v14+ and hapi v20+.
• Ensure that node support is up-to-date on engines field in package.json if present (supports node v14+).
• Ensure that node and hapi support is up-to-date on plugin requirements attribute if present (supports node v14+ and hapi v20+).
• Update JS syntax, utilizing optional chaining x?.y and nullish coalescing (x ?? y) where appropriate.
• Update dependencies.
• Add a test file esm/test.js testing the module's ESM exports.
• We decided not to do this for plugins. Add an additional explicitly-named export for each plugin, e.g. inertPlugin for inert, visionPlugin for vision, etc.