This commits adds adds "permissions" option to the test definitions
which allows tests to run with different permission sets than
the process's permission.
The change will only be in effect within the test function, once the
test has completed the original process permission set is restored.
Test permissions cannot exceed the process's permission.
You can only narrow or drop permissions, failure to acquire a
permission results in an error being thrown and the test case will fail.
This adds an exit sanitizer to ensure that code being tested or
dependencies of that code can't accidentally call "Deno.exit"
leading to partial test runs and false results.
