Remove http.target from metric attributes to control cardinality

[trask]

From @anuraaga's #4930 (comment):

For 1.10 we should go ahead and remove HTTP_TARGET from all metrics and live with it being gone until providing view configuration to javaagent users.

opentelemetry-java-instrumentation/instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/http/TemporaryMetricsView.java

Lines 98 to 101 in 25550e0

	// Use http.target when http.route is not available.
	if (!containsAttribute(SemanticAttributes.HTTP_ROUTE, startAttributes, endAttributes)) {
	fullSet = durationServerFallbackView;
	}

@jsuereth I know you had wanted http.target as a fallback since we aren't capturing http.route consistently yet, and metrics aren't nearly as useful without any route-like dimension. @mateuszrzeszutek has started the work on capturing http.route (#4852) but that work may not be finished in time for 1.10.0, so we need to make a decision on what to do in 1.10.0 release (and hopefully we'll have real solution, with http.route, in the next month or so).

[mateuszrzeszutek]

@mateuszrzeszutek has started the work on capturing http.route (#4852) but that work may not be finished in time for 1.10.0

Yep, I might not be able to finish that this week (most likely not) - the micrometer work took a lot of time to finish. Should we just remove http.target for the time being? And/or add a property that allows including it as an attribute?