Update default SLIs and examples to use `splitBy` rather than `merge`

[arthurpitman]

Currently the default SLIs of the dynatrace-service use merge and have the form:

throughput: metricSelector=builtin:service.requestCount.total:merge("dt.entity.service"):sum...
error_rate: metricSelector=builtin:service.errors.total.rate:merge("dt.entity.service"):avg..
response_time_p50: metricSelector=builtin:service.response.time:merge("dt.entity.service"):percentile(50)..
response_time_p90: metricSelector=builtin:service.response.time:merge("dt.entity.service"):percentile(90)..
response_time_p95: metricSelector=builtin:service.response.time:merge("dt.entity.service"):percentile(95)..

To produce metrics queries similar to the Data Explorer, these should be updated to use splitBy, i.e.:

throughput: metricSelector=builtin:service.requestCount.total:splitBy():sum...
error_rate: metricSelector=builtin:service.errors.total.rate:splitBy():avg...
response_time_p50: metricSelector=builtin:service.response.time:splitBy():percentile(50)...
response_time_p90: metricSelector=builtin:service.response.time:splitBy():percentile(90)...
response_time_p95: metricSelector=builtin:service.response.time:splitBy():percentile(95)...

This syntax also has the advantage of being more explicit and often more compact.

While the metrics queries produced when processing Data Explorer and Custom Charting tiles (#578), the following need updating:

• Default SLIs generated when onboarding services
• SLIs in documentation
  • https://github.com/keptn-contrib/dynatrace-service
  • https://keptn.sh/docs/0.10.x/monitoring/dynatrace/configure_slis/
• Examples: https://github.com/keptn/examples
• Full tour: https://tutorials.keptn.sh/tutorials/keptn-full-tour-dynatrace-09/index.html?index=..%2F..index#16

[j-poecher]

Since dynatrace-service has reached EOL on December 22nd, 2023, this issue has been closed.