<i18n dev> RFR: 8225641: Calendar.roll(int field) does not work correctly for WEEK_OF_YEAR [v5]

[Justin Lu]

> This PR fixes the bug which occurred when `Calendar.roll(WEEK_OF_YEAR)` rolled into a minimal first week with an invalid `WEEK_OF_YEAR` and `DAY_OF_WEEK` combo.
> 
> For example, Rolling _Monday, 30 December 2019_ by 1 week produced _Monday, 31 December 2018_, which is incorrect. This is because `WEEK_OF_YEAR` is rolled from 52 to 1, and the original `DAY_OF_WEEK` is 1. However, there is no Monday in week 1 of 2019. This is exposed when a future method calls `Calendar.complete()`, which eventually calculates a `fixedDate` with the invalid `WEEK_OF_YEAR` and `DAY_OF_WEEK` combo.
> 
> To prevent this, a check is added for rolls into week 1, which determines if the first week is minimal. If it is indeed minimal, then it is checked if  `DAY_OF_WEEK` exists in that week, if not, `WEEK_OF_YEAR` must be incremented by one.
> 
> After the fix, Rolling _Monday, 30 December 2019_ by 1 week produces _Monday, 7 January 2019_

Justin Lu has updated the pull request incrementally with five additional commits since the last revision:

 - Impl cleanup, add Saturday end day conditional
 - Rename test, clarify test documentation
 - Add type to static declaration of Cal.Builder, since only concerned with Gregorian for this test
 - Pass in amount as 1 directly
 - Reuse Calendar.Builder

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13031/files
  - new: https://git.openjdk.org/jdk/pull/13031/files/f837268c..60d0621b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13031&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13031&range=03-04

  Stats: 278 lines in 3 files changed: 132 ins; 133 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/13031.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13031/head:pull/13031

PR: https://git.openjdk.org/jdk/pull/13031