`weekdays` are incorrect for all instances of `en` locale (except US if it existed)

**Describe the bug**
`weekdays` returns `weekdays:"Sunday_Monday_Tuesday_Wednesday_Thursday_Friday_Saturday".split("_")` on all instances of `en` locale

**Expected behavior**
`weekdays` returns `weekdays:"Monday_Tuesday_Wednesday_Thursday_Friday_Saturday_Sunday".split("_")` for all instances of en locale that aren't the US. Not everyone in anglophone world is American and not everyone has backward-ass date notations.

**Information**
- latest
- N/A
- N/A
- N/A

Start by locating the locale definitions and tests for the en locale, then compare weekday ordering with the US variant described in the issue. Done means non-US en locales return Monday-first weekdays while a US locale, if supported, retains Sunday-first behavior, with coverage for the affected cases.

Written by the indexing model from the issue text.