Export data from all number systems

[movermeyer]

What are you trying to accomplish?

Fixes #89
Fixes #167

ruby-cldr was outputting number data from arbitrary number systems based on whatever data it first encountered. This resulted in the data from multiple number systems getting incorrectly mixed in the output.

What approach did you choose and why?

This is a large refactor/overhaul of the existing Numbers component.
It adds the number system as a new level of nesting in the output, and changes the key structure to more closely match the structure and terminology of the upstream CLDR data.

The Numbers component now outputs the number data for all number systems.

What should reviewers focus on?

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The impact of these changes

This is a breaking change for downstream consumers, since the key structure of the output numbers.yml files has changed significantly with this PR:

• The useless number_system key has been removed; the keys are now nested under the number system
• The keys include the standard subtype (meaning that other subtypes are now able to be exported. e.g., accounting)

Before: numbers.formats.decimal.patterns.short.1000000000
After:  numbers.latn.formats.decimal.patterns.short.standard.1000000000

Testing

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Checklist

• I have added a CHANGELOG entry for this change (or determined that it isn't needed)

[trishrempel]

Looks good; I have some minor suggestions and questions.