Prepares version 1.9.4 for release.

Release 1.9.3 (amazon-ion#423)

Bumps version to 1.9.2 (amazon-ion#417)

This is directly based on 1.9.0 due to amazon-ion#416.  It effectively reverts
the 1.9.1 release.

Prepares version 1.9.1 for release. (amazon-ion#413)

Prepares version 1.9.0 for release.

Adds GitHub workflow to detect the performance regression of ion-java…

… automatically. (amazon-ion#373)

Prepares version 1.8.2 for release.

preparing release 1.8.1

Prepare new release 1.8.0

preparing release 1.7.1 (amazon-ion#312)