[3.11] gh-104271: Fix auto() fallback in case of mixed type Enum (GH-104809)

[3.12] gh-104271: Fix auto() fallback in case of mixed type Enum (GH-104279)
(cherry picked from commit f4e2049f14d40c1b893c68530eec5e341cf3d929)

Co-authored-by: Itamar Ostricher <itamarost@gmail.com>