Add disable_badge_count parameter to the set_pusher method.

[bmarty]

The method client.set_pusher should add org.matrix.msc4076.disable_badge_count: true in the data sent to the server to let the server know that the application do not want to receive push just about updating the unread count.

This should reduce the number of Pushes that the application is receiving (with high priority) and which are at the end ignored by both Element X Android and Element X iOS.

Not sure if this parameter should be exposed in the Client API or if this can be just a hard-coded value in the SDK.

Ref:

• MSC: MSC4076: Let E2EE clients calculate app badge counts themselves (disable_badge_count) matrix-spec-proposals#4076
• Synapse impl (there is a feature flag): MSC4076: Add disable_badge_count to pusher configuration element-hq/synapse#17975