Include dispatch-val in analysis of defmethod

[mainej]

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Description

Occasionally it would be useful if the analysis included the dispatch-val of a defmethod. It's possible this could be used for #1682. Also see here for a case where clojure-lsp could use this additional analysis.

Describe the solution you'd like

Include the dispatch-val in the analysis. That value is always in the same spot, so the analysis shouldn't be too hard.

To consider:

1. Should this be opt-in, via the :analysis config?
2. dispatch-vals can be arbitrarily large. Is there a problem with size?
3. dispatch-vals can contain references to other locals and vars. Probably best to include the raw sexpr, not any transformation.

Describe alternatives you've considered

Use other tools, like rewrite-clj, to find the dispatch-val.

[mainej]

Note that :dispatch-val is a sexp. Would you rather have it be a string @borkdude? (If so, it should probably be transformed with pr-str, not str, so it's easier to identify string dispatch vals.)