[CES]: dimensions and namespace documentation

[artem-lifshits]

Summary of the Pull Request

Update CES documentation with dimension and namespace for available services.

PR Checklist

• Refers to: Can opentelekomcloud_ces_alarmrule be used/extended also for (new) Event Monitoring #1896, CES monitoring dashboard and panels #1142
• Documentation updated.
• Schema updated.
• Release notes added.

Acceptance Steps Performed

=== RUN   TestCESAlarmRule_basic
=== PAUSE TestCESAlarmRule_basic
=== CONT  TestCESAlarmRule_basic
--- PASS: TestCESAlarmRule_basic (93.75s)
=== RUN   TestCESAlarmRule_systemEvents
=== PAUSE TestCESAlarmRule_systemEvents
=== CONT  TestCESAlarmRule_systemEvents
--- PASS: TestCESAlarmRule_systemEvents (26.12s)
=== RUN   TestAccCESAlarmRules_importBasic
--- PASS: TestAccCESAlarmRules_importBasic (76.37s)
=== RUN   TestAccCheckCESV1AlarmValidation
--- PASS: TestAccCheckCESV1AlarmValidation (4.99s)
=== RUN   TestCESAlarmRule_slashes
=== PAUSE TestCESAlarmRule_slashes
=== CONT  TestCESAlarmRule_slashes
--- PASS: TestCESAlarmRule_slashes (66.77s)
PASS

Process finished with the exit code 0

[otc-zuul]

Build succeeded.
https://zuul.otc-service.com/t/eco/buildset/c0728d6997974d019b5fa2a400e8e4d7

✔️ build-otc-releasenotes SUCCESS in 3m 23s
✔️ otc-golangci-lint SUCCESS in 3m 08s
✔️ golang-make-test SUCCESS in 3m 00s
✔️ golang-make-vet SUCCESS in 2m 23s
✔️ tflint SUCCESS in 2m 00s
✔️ goreleaser-build SUCCESS in 9m 15s