These tests relied on timing between completion runs in order to check
that fast completion was working properly for completions in VFS files.
That is, they would assume that two runs happening one after another
without a sleep inbetween would always run fast completion.
However, that's not necessarily the case and there have been cases where
a dependency check happens despite its interval being fairly long
(multi-second).
This change emulates the same behaviour by changing the interval
between 0/100, which should prevent any timing issues.
Resolves rdar://72144331
This was not needed. The list of depenencies should not be changed
during fast-completion sessions.
This was also harmful because it calls stat(2) for all the dependency
files.
rdar://problem/67773257
