Set precision in MWTimeIsoParser

instead of automagically handling in ValueParsers\TimeParser

Fixes handling of input like '10. century BC'

includes partial revert of changes to test in I927209e2
(the tests were doing the right thing before that)

Change-Id: I74f88c0f629614e93bc33d4b1d893da594a0276e
Add test cases for year time parsing

actual fix is in DataValues time component, but
added tests that things also work correctly in Wikibase
time parsers.

https://github.com/DataValues/Time/pull/16

Bug: 64537
Change-Id: Ib7c698de517d226dcbc89d4c9dacd09430eb0e19
Merge "Set precision in MWTimeIsoParser"
Merge "Add test cases for year time parsing"