Add `flatMapOrKeep` to `Monad` #2698

Job	Run time
Submit Dependencies	0s
Generate Site (ubuntu-latest, temurin@17)	2m 59s
Scalafix (ubuntu-latest, temurin@8)	50s
Build and Test (ubuntu-latest, 2.12, temurin@8, rootJS)	8m 22s
Validate Steward Config (ubuntu-latest, temurin@11)	15s
Build and Test (ubuntu-latest, 2.12, temurin@8, rootJVM)	6m 59s
Build and Test (ubuntu-latest, 2.12, temurin@8, rootNative)	15m 36s
Build and Test (ubuntu-latest, 2.13, temurin@8, rootJS)	7m 44s
Build and Test (ubuntu-latest, 2.13, temurin@8, rootJVM)	6m 48s
Build and Test (ubuntu-latest, 2.13, temurin@8, rootNative)	15m 10s
Build and Test (ubuntu-latest, 2.13, temurin@17, rootJVM)	4m 32s
Build and Test (ubuntu-latest, 2.13, graalvm@17, rootJVM)	4m 22s
Build and Test (ubuntu-latest, 3, temurin@8, rootJS)	8m 29s
Build and Test (ubuntu-latest, 3, temurin@8, rootJVM)	8m 12s
Build and Test (ubuntu-latest, 3, temurin@8, rootNative)	15m 41s
Publish Artifacts	0s
	1h 45m 59s

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