initial spec updates for MP Metrics 5.0

[donbourne]

Signed-off-by: Don Bourne dbourne@ca.ibm.com

• removed references to @ConcurrentGauge
• removed references to @SimplyTimed

• removed references to @Metered

• removed references to MetricRegisty.concurrentGauge
• removed references to MetricRegistry.simpleTimer

• removed references to MetricRegistry.meter

• removed references to MetricRegistry.register methods allowing Metric implementations to be registered

• removed reference to CDI extension from Dropwizard as potential implementation

• added custom scopes / custom MetricRegistrys
• changed metrics/base to metrics?scope=base
• changed metrics/vendor to metrics?scope=vendor
• changed metrics/application to metrics?scope=application

• added requirement that scope be added to all metrics as a tag

• added recommendation to follow Open Telemetry semantic conventions for vendor metric names
• removed throughput stats from Timer

• removed mean and stddev from Timer and Histogram

• replaced Future Direction with description of what we're trying to make it easy to implement with popular metrics libraries

• added initial API changes for 5.0 to breaking changes

[jgallimore]

I think this looks great. Do we want to keep the JSON format examples for the REST endpoints?

[donbourne]

I think this looks great. Do we want to keep the JSON format examples for the REST endpoints?

Removal of that should get addressed when we handle issue #685 .