Test: Use language selector in JSON to notify about too many folding reanges

[aeschli]

Refs: #142496

• anyOS @rzhao271
• anyOS @joaomoreno

Complexity: 2

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Instead of notifications, for JSON we now use the language selector to inform when we limited folding range, document symbols or color decorator.

• In the settings change json.maxItemsComputed to a smaller number to easiert test this
• Create JSON files with lots of folding ranges, lot's of properties and lots of color decorators*
• Verify that the language indicator shows when symbols have been limited.

• color decorators appear at places where the associated JSON schema declares a value as a color value. The easiest way to test is to open a color-theme.json file, e.g. here