Mp metrics2x

[evelinec]

Update guide to mpMetrics-2.0 according to issues raised in OpenLiberty/guides-common#224, #50.

Specific changes:

• Updated metric outputs where the formats are different, ie, @Gauged, @Counted and some base metric outputs
• Added Liberty vendor metrics
• Updated @Countered annotation description to be counting monotonically upwards only
• Added tags for the @Timed annotation to demonstrate multi-dimension metrics
• Added description of the multi-dimension metrics with tag and updated guide accordingly
• Updated the start directory

[gkwan-ibm]

• suggest the description of @Timed of get()
  description = "Time needed to get the properties of a system"

• suggest the description of @Timed of list()
  description = "Time needed to create an inventory list of systems"

• the output from 90 to 97 can be better as

# TYPE application_inventoryProcessingTime_rate_per_second gauge
application_inventoryProcessingTime_rate_per_second{method="get"} 0.0019189661542898407
...
# TYPE application_inventoryProcessingTime_seconds summary
# HELP application_inventoryProcessingTime_seconds Time needed to get the properties of a system
application_inventoryProcessingTime_seconds_count{method="get"} 1
application_inventoryProcessingTime_seconds{method="get",quantile="0.5"} 0.127965469
...
# TYPE application_inventoryProcessingTime_rate_per_second gauge
application_inventoryProcessingTime_rate_per_second{method="list"} 0.0038379320982686884
...
# TYPE application_inventoryProcessingTime_seconds summary
# HELP application_inventoryProcessingTime_seconds Time needed to create an inventory list of systems
application_inventoryProcessingTime_seconds_count{method="list"} 2
application_inventoryProcessingTime_seconds{method="list",quantile="0.5"} 2.2185000000000002E-5
...

[evelinec]

Addressed review feedback. We need to have the same name and description for the tagged annotation to work. We can't change the descriptions as suggested, unless they're the same.

@gkwan-ibm can you review again? Thank you.

[evelinec]

@Channyboy Hi David, can you help SME review the changes make to update the metrics guide to mpMetrics-2.0? Detail changes described in the PR description. Thank you.

[evelinec]

@yeekangc Can you review this PR as well pls? Thank you.

[evelinec]

Updated Liberty vendor doc link to the online doc, as OpenLiberty/docs#684 is being worked on already.

[evelinec]

Merged to QA.