prepare for 8.2.0 release

Signed-off-by: Ian Chen <ichen@openrobotics.org>

Prepare for 8.1.1 release (gazebosim#664)

* Prepare for 8.1.1 release

Signed-off-by: Carlos Agüero <caguero@openrobotics.org>
Co-authored-by: Steve Peters <scpeters@openrobotics.org>

Prepare for 7.5.2 (gazebosim#658)

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>

Prepare for 8.1.0 release (gazebosim#650)

Signed-off-by: Michael Carroll <mjcarroll@intrinsic.ai>
Signed-off-by: Michael Carroll <carroll.michael@gmail.com>
Co-authored-by: Shameek Ganguly <shameek@intrinsic.ai>

Prepare for 8.1.0 release (gazebosim#650)

Signed-off-by: Michael Carroll <mjcarroll@intrinsic.ai>
Signed-off-by: Michael Carroll <carroll.michael@gmail.com>
Co-authored-by: Shameek Ganguly <shameek@intrinsic.ai>

Prepare for 8.0.0 (gazebosim#633)

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>

Prepare for 8.0.0 pre1 release (gazebosim#625)

Signed-off-by: Ian Chen <ichen@openrobotics.org>

Prepare for 7.5.1 (gazebosim#623)

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>

Prepare for 7.5.0 (gazebosim#599)

Signed-off-by: Benjamin Perseghetti <bperseghetti@rudislabs.com>

Prepare for 7.4.0 (gazebosim#583)

Signed-off-by: Addisu Z. Taddese <addisu@openrobotics.org>