vectorstores: Allow configuring the chroma vector store by setting a configured instance of *chromago.Client

[bilal-bhatti]

As the title says:

Allow configuring the chroma vector store by setting a configured instance of *chromago.Client.

The chromago.Client allows additional configuration that is currently not possible, such as auth, headers etc. Allowing a configured client instance to be set as an option would unlock a richer set of configuration options.