Allow loading add-ons from multiple Node.js instances if they are
declared context-aware; in particular, this applies to N-API addons.

Also, plug a memory leak that occurred when registering N-API addons.

Refs: https://github.com/nodejs/node/pull/23319

PR-URL: https://github.com/nodejs/node/pull/26175
Fixes: https://github.com/nodejs/node/issues/21481
Fixes: https://github.com/nodejs/node/issues/21783
Fixes: https://github.com/nodejs/node/issues/25662
Fixes: https://github.com/nodejs/node/issues/20239
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

Partition test/addons-napi into test/js-native-api and test/node-api to
isolate the Node.js-agnostic portion of the N-API tests from the
Node.js-specific portion.

PR-URL: https://github.com/nodejs/node/pull/24557
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>