[release/v2.12.x] Prepare release 2.12.0 (open-telemetry#13056)

[release/v2.11.x] Prepare release 2.11.0 (open-telemetry#12959)

[release/v2.10.x] Prepare release 2.10.0 (open-telemetry#12620)

[release/v2.9.x] Prepare release 2.9.0 (open-telemetry#12460)

[release/v2.8.x] Prepare release 2.8.0 (open-telemetry#12247)

Modify workflow to complete 1.33.6 release (open-telemetry#12111)

[release/v2.7.x] Prepare release 2.7.0 (open-telemetry#12036)

Co-authored-by: Lauri Tulmin <ltulmin@splunk.com>

[release/v1.33.x] Prepare release 1.33.5 (open-telemetry#11903)

[release/v2.6.x] Prepare release 2.6.0 (open-telemetry#11838)

Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>

[release/v1.33.x] Prepare release 1.33.4 (open-telemetry#11626)