Standard naming scheme for feature flags to increase clarity

[indrora]

Discussed in #12576

^{Originally posted by efenderbosch January 18, 2021}
It is easy to understand what the aws-cdk:enableDiffNoFail feature flag does.

However, feature flag names like aws-cdk/secretsmanager:parseOwnedSecretName are unclear. I don't know by reading the flag name if if enabling the flag will include or exclude the suffix. A better name for this flag might be aws-cdk/secretsmanager:excludeSecretNameSuffix.