Upgrade to Micrometer 1.6.0

[snicoll]

Micrometer 1.6 has a number of improvements that may require some change on our end:

• Support for CloudWatch's highResolution property (Support of high resolution metrics for CloudWatch micrometer-metrics/micrometer#2088)
• Metrics support for Okhttp (added metrics for OkHttp connection pool micrometer-metrics/micrometer#2066)
• Commons Pool2 metrics (apache commons pool2 statistics micrometer-metrics/micrometer#1711)

There is also the SLO meter registry for which we have a PR

[snicoll]

There is no obvious candidate for automatic instrumentation for Okhttp and commons pool2. We don't really have auto-configuration for the former and the latter is wrapped as an implementation detail of the redis driver and the ActiveMQ connection factory.

[snicoll]

Support for CloudWatch's highResolution property

That one is in Spring Cloud AWS so nothing we can do here.