vBeta v12 release.

Update exporter package names

Change package names from "ext" to "exporter" (#953)
opentelemetry-ext-datadog -> opentelemetry-exporter-datadog
opentelemetry-ext-jaeger-> opentelemetry-exporter-jaeger
opentelemetry-ext-opencensusexporter-> opentelemetry-exporter-opencensus
opentelemetry-ext-otlp-> opentelemetry-exporter-otlp
opentelemetry-ext-prometheus-> opentelemetry-exporter-prometheus
opentelemetry-ext-zipkin-> opentelemetry-exporter-zipkin

Update instrumentation package names

Change package names from "ext" to "instrumentation" (#961, #966, #969)
opentelemetry-ext-aiohttp-client-> opentelemetry-instrumentation-aiohttp-client
opentelemetry-ext-asgi-> opentelemetry-instrumentation-asgi
opentelemetry-ext-asyncpg-> opentelemetry-instrumentation-asyncpg
opentelemetry-ext-boto-> opentelemetry-instrumentation-boto
opentelemetry-ext-botocore-> opentelemetry-instrumentation-botocore
opentelemetry-ext-celery-> opentelemetry-instrumentation-celery
opentelemetry-ext-dbapi-> opentelemetry-instrumentation-dbapi
opentelemetry-ext-django-> opentelemetry-instrumentation-django
opentelemetry-ext-elasticsearch-> opentelemetry-instrumentation-elasticsearch
opentelemetry-ext-flask-> opentelemetry-instrumentation-flask
opentelemetry-ext-grpc-> opentelemetry-instrumentation-grpc
opentelemetry-ext-jinja2-> opentelemetry-instrumentation-jinja2
opentelemetry-ext-mysql-> opentelemetry-instrumentation-mysql
opentelemetry-ext-opentracing-shim-> opentelemetry-instrumentation-opentracing-shim
opentelemetry-ext-psycopg2-> opentelemetry-instrumentation-psycopg2
opentelemetry-ext-pymemcache-> opentelemetry-instrumentation-pymemcache
opentelemetry-ext-pymongo-> opentelemetry-instrumentation-pymongo
opentelemetry-ext-pymysql-> opentelemetry-instrumentation-pymysql
opentelemetry-ext-pyramid-> opentelemetry-instrumentation-pyramid
opentelemetry-ext-redis-> opentelemetry-instrumentation-redis
opentelemetry-ext-requests-> opentelemetry-instrumentation-requests
opentelemetry-ext-sqlalchemy-> opentelemetry-instrumentation-sqlalchemy
opentelemetry-ext-sqlite3-> opentelemetry-instrumentation-sqlite3
opentelemetry-ext-system-metrics-> opentelemetry-instrumentation-system-metrics
opentelemetry-ext-wsgi-> opentelemetry-instrumentation-wsgi

opentelemetry-api

• Update environment variable names, prefix changed from OPENTELEMETRY to OTEL (#904)
• Stop TracerProvider and MeterProvider from being overridden (#959)

opentelemetry-sdk

• Changed default Sampler to ParentOrElse(AlwaysOn) (#960)
• Update environment variable names, prefix changed from OPENTELEMETRY to OTEL (#904)
• Implement Views in metrics SDK (#596)
• Update environment variable OTEL_RESOURCE to OTEL_RESOURCE_ATTRIBUTES as per the specification (#973)

opentelemetry-instrumentation-django

• Update environment variable names, prefix changed from OPENTELEMETRY to OTEL (#904)

opentelemetry-instrumentation-elasticsearch

• Update environment variable names, prefix changed from OPENTELEMETRY to OTEL (#904)

opentelemetry-instrumentation-flask

• Update environment variable names, prefix changed from OPENTELEMETRY to OTEL (#904)

opentelemetry-instrumentation-pyramid

• Update environment variable names, prefix changed from OPENTELEMETRY to OTEL (#904)

opentelemetry-instrumentation-redis

• Update default SpanKind to SpanKind.CLIENT (#965)