Remove Old SDK and dependent code on that SDK (#2802)

* Remove prometheus example code

* Remove prometheus exporter code

* Remove stdoutmetric code

* Remove sdk/metric/* packages

* Remove opencensus example code

* Remove otlpmetric exporter code

* Remove OpenCensus bridge code

* go mod tidy

* Remove empty modules

.github/dependabot.yml

@@ -19,24 +19,6 @@ updates:
     schedule:
       interval: weekly
       day: sunday
-  - package-ecosystem: gomod
-    directory: /bridge/opencensus
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
-  - package-ecosystem: gomod
-    directory: /bridge/opencensus/test
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
   - package-ecosystem: gomod
     directory: /bridge/opentracing
     labels:
@@ -73,15 +55,6 @@ updates:
     schedule:
       interval: weekly
       day: sunday
-  - package-ecosystem: gomod
-    directory: /example/opencensus
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
   - package-ecosystem: gomod
     directory: /example/otel-collector
     labels:
@@ -100,15 +73,6 @@ updates:
     schedule:
       interval: weekly
       day: sunday
-  - package-ecosystem: gomod
-    directory: /example/prometheus
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
   - package-ecosystem: gomod
     directory: /example/zipkin
     labels:
@@ -136,33 +100,6 @@ updates:
     schedule:
       interval: weekly
       day: sunday
-  - package-ecosystem: gomod
-    directory: /exporters/otlp/otlpmetric
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
-  - package-ecosystem: gomod
-    directory: /exporters/otlp/otlpmetric/otlpmetricgrpc
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
-  - package-ecosystem: gomod
-    directory: /exporters/otlp/otlpmetric/otlpmetrichttp
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
   - package-ecosystem: gomod
     directory: /exporters/otlp/otlptrace
     labels:
@@ -190,24 +127,6 @@ updates:
     schedule:
       interval: weekly
       day: sunday
-  - package-ecosystem: gomod
-    directory: /exporters/prometheus
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
-  - package-ecosystem: gomod
-    directory: /exporters/stdout/stdoutmetric
-    labels:
-      - dependencies
-      - go
-      - Skip Changelog
-    schedule:
-      interval: weekly
-      day: sunday
   - package-ecosystem: gomod
     directory: /exporters/stdout/stdouttrace
     labels: