Add a snippet demonstrating a stale read.

[jlara310]

We need a Firestore snippet that demonstrates how to set read options to perform a stale read. A stale read can improve latency for request that don't require strong consistency.

File to update:

https://github.com/googleapis/java-firestore/blob/main/samples/snippets/src/main/java/com/example/firestore/snippets/ManageDataSnippets.java

[MarkDuckworth]

@jlara310, can you provide some additional information about what java-firestore API the snippet should demonstrate? I'm not familiar with stale reads and I can't find an API member that looks relevant.

[jlara310]

@MarkDuckworth , thank for the quick reply! I started a PR for this in #1273. This snippet is very similar to this one but the use case is performance instead of data recovery.

[MarkDuckworth]

@jlara310, Okay, it seems like you are implementing this, so I'm going to re-assign this issue to you. Assign back if I misunderstood. BTW, the PR looks good so far. Feel free to add me as a reviewer when it is ready.