…operations.

Relativize paths returned from notify to the build_root.
Refactor invalidate method to be an associated method on the
InvalidationWatcher.

* Use spawn on io pool instead of custom future impl
* Write python fs tests
* Relativize paths to invalidate to build root
* invalidate nodes with parent paths.
* Comments

Make some things public so we can use them in tests.
Use canonical path to build root for relativizing changed paths.

Return watch errors as core::Failure all the way to user.
Check notify event type when deciding whether to invalidate parents.
Move task executor onto invalidation watcher.
Move test_support trait impl into test_support mod.

…lazy

with file watching. Format watch and nodes files.

[ci skip-jvm-tests]  # No JVM changes made.

…t interfere"

This reverts commit 974b3ce.

[ci skip-jvm-tests]  # No JVM changes made.

# Delete this line to force CI to run the JVM tests.
[ci skip-jvm-tests]  # No JVM changes made.

# Delete this line to force CI to run the JVM tests.
[ci skip-jvm-tests]  # No JVM changes made.

# Delete this line to force CI to run the JVM tests.
[ci skip-jvm-tests]  # No JVM changes made.

# Delete this line to force CI to run the JVM tests.
[ci skip-jvm-tests]  # No JVM changes made.

build root at startup. On Linux watch individual directory roots.

[ci skip-jvm-tests]  # No JVM changes made.