fix: Accept any numeric tracking event value

[kinyoklion]

track threw a ClassCastException for a tracking event value which was not a Double.

• TrackingEventDetails.getValue() is an Optional<Number>, so new MutableTrackingEventDetails(99) (an Integer) reached the provider and failed the (Double) cast before any event was sent.
• The value is now converted with Number.doubleValue(), which is what the LaunchDarkly trackMetric API takes.
• Added a test tracking an integer value.

Implementation details

The OpenFeature Java SDK does not constrain the numeric type an application passes, and MutableTrackingEventDetails stores the Number as given, so any of Integer, Long, Float, or BigDecimal reached the cast. Only Double worked.

Testing: the change is covered by ProviderTest.itCanTrackAnIntegerTrackingEventValue. The test suite could not be run on this machine because Maven Central and the Gradle plugin portal answered dependency resolution with HTTP 429 from this network; CI runs the suite.

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Open in Devin Desktop: https://app.devin.ai/desktop/session/fe1eb757fe694ef79f3d09f6307d4b47?variant=devin
Requested by: @kinyoklion

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