Metrics should not require manual enabling

[sighphyre]

Describe the feature request

This SDK requires manually opting into metrics. This is different from other Unleash SDKs

Background

This is very easy to miss and if you're used to using other Unleash SDKs, you won't notice that you've missed it

Solution suggestions

Make this opt out instead

[gastonfournier]

The new SDK has metrics enabled by default: https://github.com/Unleash/unleash-android/blob/main/docs/MigrationGuide.md