Allow configuration of which RPC events are reported as spans

[MatthewVaadin]

Currently, there are many RPC events reported that may not be that useful (such as the opened-changed event for dropdown boxes). There should be a way for the developer to configure which events are reported and which are not. The defaults for these should be chosen to be useful, but not verbose.

[heruan]

Still relevant after the 5.0 Micrometer rewrite. Each RPC invocation gets a vaadin.rpc observation with vaadin.rpc.event and vaadin.rpc.component as high cardinality attributes, and there is no way to exclude events. Re-scoped for 5.0: add a setting in ObservabilitySettings and ObservabilityProperties (for example a list of event names to ignore) and apply it in RpcMetricsBinder. See also #53, which would likely be covered by the same filter.