Use libloading to load the TSS libraries

[hug-dev]

We currently link the TSS libraries at compile time, it would be nice to be able to load them at runtime, through a constructor option.
There could be a feature flag to choose one of the two options.

[hug-dev]

I am thinking of doing this using pkg-config:

• pkg-config helps us find the library and header files on the system
• bindgen generates a binding files for those header files
• we list (by-hand) the function pointers types and symbol names that we want to dynamically load
• the build script sets up an environment variable for the TSS libraries location so that the constructors can read it to load them

[hug-dev]

It would actually be a better idea to just have the pkg-config library finding but to still dynamically link it at compile time.
It makes little sense for this crate to use libloading as of today.