Prep v1.5 release branch (#2041)

* Prep main for v1.5.0-rc.0

* Prep release branch for v1.5.0-rc.0

Author: thampiotr

CHANGELOG.md

@@ -7,7 +7,7 @@ This document contains a historical list of changes between releases. Only
 changes that impact end-user behavior are listed; changes to documentation or
 internal API changes are not present.
 
-Main (unreleased)
+v1.5.0-rc.0
 -----------------
 
 ### Breaking changes