Restrictions on calling H5I functions on "library types" should be relaxed

**Is your feature request related to a problem? Please describe.**
Several H5I functions cannot be called on ID types which are considered "library types", which is essentially any ID type in the `H5I_type_t` enumeration. These restrictions don't necessarily always make sense and can be a hindrance. One example of this is that the function `H5Inmembers()` cannot be used to quickly determine the number of HDF5 IDs of a particular type that are still open. However, the `H5Iiterate()` function can be called on any ID type and can effectively give the same desired result as `H5Inmembers()`, though a bit more awkwardly due to needing to supply an iteration callback function.

**Describe the solution you'd like**
These restrictions should be relaxed so that at least "read-only" functions can be called on ID types that are in the `H5I_type_t` enumeration.