[release/v1.30.0] Prepare release 1.30.0 (open-telemetry#147)

* Prepare release 1.30.0

* Update changelog entry to include -rc.1 suffix

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Co-authored-by: Jack Berg <[email protected]>

Prepare release 1.29.0 (open-telemetry#125)

Prepare release 1.28.0 (open-telemetry#93)

Prepare release 1.27.0 (open-telemetry#85)

Prepare release 1.26.0 (open-telemetry#80)

Prepare release 1.25.0 (open-telemetry#65)

Prepare release 1.24.0 (open-telemetry#59)

Prepare release 1.23.1 (open-telemetry#38)

Prepare release 1.22.0 (open-telemetry#33)

Prepare release 1.21.0 (#18)