Use cumulative temporality metrics by default

[a-thaler]

Description

For metrics there is the concept of temporality which is also respected by OTEL. There are pros and cons for both, however in OTEL it was decided that the default setting for SDKs is cumulative.

As outlined in the readme of the telemetry plugin, the plugin sets by default the metric temporality to "delta". That is an unexpected behaviour and it will take some time to figure that out (in case you missed that block in the readme).
To avoid surprises, I suggest to change the default for the standard kinds like "to-otlp" to "cumulative" and only enable delta preference for kinds which explicitly require them (for example "to-dynatrace")

Tasks:

• Change default to "cumulative" for all
• Document how to change the preference to "delta"
• Configure "delta" preference for dynatrace kind implicitly and document it
• Document the breaking change in the release notes