[xdl] fix analytics for expo start

[esamelson]

This PR fixes an issue with expo-cli@3.22.x where the number of logged Start Project and Serve Manifest events are significantly lower than expected.

Paired with @animeeples to investigate and we found the root cause to be that by the time the Serve Manifest event should be sent, the _userId field in Analytics.ts is not set, meaning the following statement evaluates to false and the event is never sent to segment:

expo-cli/packages/xdl/src/Analytics.ts

Line 41 in d7e4d4d

if (_segmentNodeInstance && _userId) {

Following the chain of methods that set the _userId field, it looks like this issue was introduced by 553eb01 which eliminated a call to UserManager.ensureLoggedInAsync() (553eb01#diff-bf9f0db58154788a372e25a5c3898adbL2009). This method will set the _userId field on Analytics.ts if it is not already set.

This PR restores the previous functionality by adding a call to UserManager.ensureLoggedInAsync() in the analogous location, in order to keep these two metrics the same as before and preserve comparisons to historical data.

Looking further ahead, it would be good to

• refactor this code to be more intentional about when we set the _userId field in Analytics, so it's not such a hidden side effect
• reevaluate whether or not we want to track any/all segment events for users who are not logged in

But this PR is a first step/quick fix to get the metrics back to the place they were before 3.22.0.