Retry manifest file loading only in dev mode (#73900)
In #73891 we added another manifest to be loaded in `loadComponents`
(initially unconditionally). This uncovered a flakiness in prod mode
when attempting to load an optional manifest. The non-existent manifest
is attempted to be loaded three times with 100ms delay between attempts,
before giving up. For some reason the increased loading time leads to
more test flakiness.
To mitigate this, we're limiting the retry behaviour to the dev mode,
which matches the original intention when this was introduced in #45244.
