Summary
-------

Implement Era.getDisplayName() in each subclass of Era.

Problem
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The default implementation of Era.getDisplayName doesn't work with non-IsoChronology because DateTimeFormatterBuilder.TextPrinterParser.format fails to get the Chronology of the Era.

Solution
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In each subclass/enum of java.time.chrono.Era, override Era.getDisplayName() and return appropriate display name for the era, depending on its style and locale.

Specification
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In java.time.chrono.{Hijrah|ThaiBuddhist|Minguo}Era enums, add the following method:

    /**
      * {@inheritDoc}
      *
      * @param style {@inheritDoc}
      * @param locale {@inheritDoc}
      */
    @Override
    public String getDisplayName(TextStyle style, Locale locale)