[BEAM-1871] Hide internal implementation details of how we create a DefaultBucket for GCP Temp Location

[lukecwik]

Moved relevant contents of GcpProjectUtil and DefaultProject into GcpOptions.GcpTempLocation

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[lukecwik]

I kept this as a marker interface incase we do add transport level options for CRM.
It also gives clarity as to what pipeline options it relies on.

[lukecwik]

R: @dhalperi @tgroh

[coveralls]

Coverage increased (+0.001%) to 69.794% when pulling 270dfc2 on lukecwik:thin_sdk_core3 into fdf2de9 on apache:master.

[dhalperi]

LGTM, high-level scan only.

Analysis: Looks like a lot of moves. Spot-checked a few things and checked out.

4 files deleted, so -80 lines of license doesn't quite explain -200 lines overall. But another 10-15 of imports, plus some condensed testing does.

[dhalperi]

self-merge at will.