[libfabric-users] release candidate v1.15.2rc1 now available

[Hefty, Sean]

I started the v1.15.2 release cycle.  RC1 is now available:

https://github.com/ofiwg/libfabric/releases/tag/v1.15.2rc1

Maintainers, please update NEWS.md with a list of fixes since v1.15.1.  Also, if there are other fixes in main to cherry pick, please do so prior to rc2 (targeting the middle of next week if one is needed).

- Sean