updateLocale also sets locale

[pachewise]

Describe the bug
calling updateLocale also sets the locale globally. I would expect this operation to not change moment state, other than updating the locale we are working with. In particular, the order in which we called updateLocale would determine which was the "default" locale.

To Reproduce
Steps to reproduce the behavior:

1. set a locale: moment.locale('en');
2. call moment.defineLocale('your-locale', {});
3. Locale will now be 'your-locale'

Expected behavior
Locale would remain 'en'.

Screenshots
N/A

Desktop (please complete the following information):
N/A

Smartphone (please complete the following information):
N/A

Moment-specific environment
N/A

Please run the following code in your environment and include the output:

console.log((new Date()).toString())
console.log((new Date()).toLocaleString())
console.log((new Date()).getTimezoneOffset())
console.log(navigator.userAgent)
console.log(moment.version)

Thu Mar 12 2020 15:00:21 GMT-0700 (Pacific Daylight Time)
3/12/2020, 3:00:21 PM
420
Mozilla/5.0 (darwin) AppleWebKit/537.36 (KHTML, like Gecko) jsdom/15.2.1
2.24.0

Additional context
Found issue running jest+enzyme snapshot tests on our code

[marwahaha]

related to moment/momentjs.com#581

[Kartik18g]

Hey, Will you guys be accepting this PR by "DakCrowder" , if not can i work on this and create my own PR.

[marwahaha]

@Kartik18g I would not recommend working on this since there is already an open PR. Thanks for considering.

[marwahaha]

Changing this behavior may surprise many existing Moment.js users. This functionality is documented at https://momentjs.com/docs/#/customization/ .

See also https://momentjs.com/docs/#/-project-status/

[plandem]

so we had moment.locale(code, settings) that changes current locale and now we got another way moment.updateLocale(code, settings), but still no way to dynamically load locale without changing current one?!