ARCH-1192 - Switch to pr_target & add descriptions for use

[danielle-casella-adams]

Summary of PR changes

• In the increment-version-on-merge workflow switch to using the pull_request_target so when it is merged it will have the correct permissions to create and push a new version tag on the repo.
• The descriptions of pull_request/pull_request_target have been updated so reviewers should know which scenarios each should be used in the workflows.
• The version of the action has not been updated on the readme's since this change won't affect the usage.
  • When I have some time to implement the readme version update on merge all of the versions should be reconciled.

[jsclifford]

LGTM