Adding the Metrics Counter API (#1578)
Adding the Metrics Counter API (#1578)

* counter API

* fix link

* clarify unit and description

* address review comments

* avoid money

* move the counter creation example to the right place

* update the example to avoid anything related to billing/accounting

* mention that BMP is basically utf8mb3

* Update specification/metrics/new_api.md

Co-authored-by: Leighton Chen <fc3915c589827d8c520f66f2c36dd2a5b4f0521e@microsoft.com>

* Update specification/metrics/new_api.md

Co-authored-by: Leighton Chen <fc3915c589827d8c520f66f2c36dd2a5b4f0521e@microsoft.com>

* Update specification/metrics/new_api.md

Co-authored-by: Leighton Chen <fc3915c589827d8c520f66f2c36dd2a5b4f0521e@microsoft.com>

* explain why 63 was chosen for unit string length

Co-authored-by: Leighton Chen <fc3915c589827d8c520f66f2c36dd2a5b4f0521e@microsoft.com>
Co-authored-by: Bogdan Drutu <3f8e17047c2434e5c82a61403e56b9ef3e226d99@gmail.com>
open-telemetry/opentelemetry-specification,open-telemetry/opentelemetry-specification