Add support to always track feature events

[edvinerikson]

Is your feature request related to a problem? Please describe.
We want to track all feature evaluations by default, currently its only possible to configure this through the LD UI per flag basis.

Describe the solution you'd like
Add a new config option trackEvents: booleanin the SDK init that allows us to always generate the feature event.
https://github.com/launchdarkly/js-client-sdk/blob/master/packages/launchdarkly-js-sdk-common/src/index.js#L172

Describe alternatives you've considered
We've considered forking the event collector, but I feel that its a lot of code to maintain cross SDK vs just adding the option here.

Additional context
We will also need the same option in the java server, node server and node client SDK.

[eli-darkly]

The place to configure this isn't on the SDK side, but on the dashboard. If you look at the form that comes up when you click Edit for an environment in Settings, there's this option:

That turns on full event tracking for all flags in the environment by default. Or have I misunderstood what you're asking for?

[edvinerikson]

Missed that, thanks 👍