Basic support for dynamic indentation

[rrudakov]

This PR introduces clojure-ts-get-indent-function variable, which can be set by CIDER as:

(setq-local clojure-ts-get-indent-function #'cider--get-symbol-indent)

to enable dynamic indentation based on :style/indent metadata. Currently it supports only first level, so {:style/indent 1} and {:style/indent [1 [[:defn]] :form]} are both translated to (:block 1) rule.

I haven't added anything to README, because it's internal change, similar function is not mentioned in clojure-mode readme as well.

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[bbatsov]

The change looks pretty good overall! We're now one step closer to full support for CIDER!