fs: improve errors thrown from fs.watch()

• Add an accessor property initialized to FSEventWrap to check the state of the handle from the JS land
• Introduce ERR_FS_WATCHER_ALREADY_STARTED so calling start() on a watcher that is already started will throw instead of doing nothing silently.
• Introduce ERR_FS_WATCHER_NOT_STARTED so calling close() on a watcher that is already closed will throw instead of doing nothing silently.
• Validate the filename passed to fs.watch()
• Assert that the handle in the watcher are instances of FSEvent instead of relying on the illegal invocation error from the VM.
• Add more assertions in FSEventWrap methods now that we check initialized and the filename in JS land before invoking the binding.
• Use uvException instead of errornoException to create the errors with the error numbers from libuv to make them consistent with other errors in fs.

TODO:

• Improve fs.watchFile() the same way this patch improves fs.watch()
• It seems possible to fire both rename and change event from libuv together now that we can check if the handle is closed via initialized in JS land.

This is a retake of https://github.com/nodejs/node/pull/17851

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

fs