Reapply "Have Glean stable views parse datetime metrics as timestamps (bug 1771733) (#3343)"

[sean-rose]

This reapplies #3343, which was temporarily reverted in #3394 because it had the unfortunate side effect of causing the search_derived.mobile_search_clients_daily_v1 ETL query to exceed the query complexity limit in the moz-fx-data-shared-prod project (bug 1803534).

Now the query complexity limit in the moz-fx-data-shared-prod project has been increased, and I've confirmed that the search_derived.mobile_search_clients_daily_v1 ETL won't exceed the query complexity limit with this change applied.

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Checklist for reviewer:

• Commits should reference a bug or github issue, if relevant (if a bug is referenced, the pull request should include the bug number in the title).
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• If adding a new field to a query, ensure that the schema and dependent downstream schemas have been updated.
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