Issue in ELBO estimation perhaps due to Likelihood initialization
I wanted to use the \`estimate_evidence_lower_bound()\` method, but I got this error:
```
AttributeError: type object 'NoValue' has no attribute 'dtype'
```
when the routines tries to access the \`likelihood.target.dtype\` (as well as later for \`likelihood.lsm_tangents_shape.size\`).
My likelihood is built from two terms, one \`VariableCovarianceGaussian\` term and one \`Gaussian\` term, but each of these two terms individually seem to have the same initialization problem. It seems that their \`domain\` and \`lsm_tangents_shape\` attributes remain the default \`NoValue\`, which causes a problem in the ELBO estimation routine.
\[edit: the creation of a new branch below was a mistake\]
issue