Add new CAF_ADD_TYPE_ID_FROM_EXPR macro
Add new CAF_ADD_TYPE_ID_FROM_EXPR macro

The macro CAF_ADD_TYPE_ID expects a fully qualified type name that it
can prefix with "::". However, declaring types from type expression,
e.g., via `decltype` requires users to work around this limitation with
a type alias. The new macro renders workarounds obsolete by accepting
any expression that results in a type.

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