Adjust schedule for long-running Java ValidatesRunner Dataflow Streaming variants

[Abacn]

These tests run more than 8 hrs for now, and subsequent running is blocked until the previous one finished

There are three variants of PostCommit Java ValidatesRunner Dataflow (v1) Streaming. Make each one run daily and with 8 h offset. Then,

• If there is a regression in Beam (including worker jar), we can still get 8h bisect window.

• If it's a regression in one of the variant, by comparing with the other two variants, we can still get signal after 8 hr, same as now

• Bump Runner v2 variant running internval to 12 h.

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[Abacn]

R: @arunpandianp

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