npmInstall up-to-date check broken with fastNpmInstall

I stumbled on a weird issue with the following steps:

1. Fresh git checkout, i.e. no node_modules directory present
2. Run task npmInstall with the fastNpmInstall option enabled
3. Run the clean task, i.e. remove the whole node_modules directory
4. Run npmInstall again, it reports as up-to-date
5. Other tasks fail because node_modules is missing

The problem is that in step 2 the file node_modules/.package-lock.json was not recorded as output because it did not yet exist at configuration time, only after task execution. So the task has no configured outputs and won't become out of date by removing the node_modules directory.

Proposed fix: When using fastNpmInstall, do not check for existance of the file at configuration time here, instead always return the file.

Start in src/main/kotlin/com/github/gradle/node/npm/task/NpmInstallTask.kt around line 115 and inspect how fastNpmInstall determines its outputs. Reproduce the npmInstall, clean, and npmInstall sequence, then verify that removing node_modules makes the task out of date and restores the directory on execution.