Ability to add `external-serverless` instances via user interface

 User story:

• As a PMM admin user I need to be able to add to monitoring the Remote Service where I don't have PMM Agent running on its node so that I will be able to collect it's Prometheus compatible metrics

UI/UX:

1)

Add Instance landing page: 

Remote Service

Add a remote Service

 

2) Add Instance page 

Note: list  of fields based on "pmm-admin  add external-serverless" command

 

Acceptance criteria

• User able to specify parameters to it's Prometheus compatible endpoint exposing metrics to PMM
• Fields in form have tooltips for an explanation on fields (see pmm-admin command )
• data collected by PMM and available in advanced data exploration dashboard

Out of scope:

• TBD

Suggested implementation:

How to test:

Details:
UI  for PMM-5765