Remove invalid asserts on unsupported underlying enum type (dotnet/coreclr#9192)

Remove invalid asserts on unsupported underlying enum type (dotnet/coreclr#9192)

The underlying enum type can be floating point type or native integer for historic reasons.
However, not all framework methods support these special enum types. They should throw exception
for them instead of asserting.

Fix issue dotnet/coreclr#7670

Commit migrated from https://github.com/dotnet/coreclr/commit/fbe52109370516c19e47451040752305d5dc0fe0