Updated operation streams parameter definitions

[jlstevens]

Running the Large Data notebook on current master revealed a param bug (holoviz/param#455) where decimate was failing despite having a valid declaration.

The issue is that #4818 generalized the allowable values for the streams parameter but the param bug referenced above means that all operations need to use the same ClassSelector definition even if the current declaration is a valid subset of what is accepted by the base class (i.e param.List or param.Dict).

I realize that I probably updated a bunch of parameter definitions in #4818 even though it wasn't strictly necessary (if the param bug wasn't an issue).

It is important to fix this param issue as all user defined operations will also be affected: users shouldn't have to update their streams parameter definitions.

[jlstevens]

@philippjfr I've grepped for streams definitions everywhere and can't see any more operations that need updating. Happy to merge?