Extract Clojure compilation error handling into cider-compilation.el

[bbatsov]

Pull the ~500-line compilation-error handling subsystem out of cider-eval.el into its own module. cider-compilation sits below cider-eval in the layering: it turns nREPL eval-error / stacktrace responses into the *cider-error* buffer, source overlays, and inline messages.

Moved:

• User-tunable knobs: cider-show-error-buffer, cider-auto-jump-to-error, cider-auto-select-error-buffer, cider-error-highlight-face, cider-warning-highlight-face, cider-inline-error-message-function, cider-clojure-compilation-error-phases (+ its default).
• Parsing and rendering: cider-clojure-compilation-regexp, cider-module-info-regexp, cider-compilation-regexp, cider-extract-error-info, cider-handle-compilation-errors, cider--display-error-unobtrusively, cider--handle-stacktrace-response, cider--analyze-last-stacktrace, the cider-default-err-*-handler family, cider--handle-err-eval-response, cider--clojure-{1.10-error,1.10-location,warning}, cider--render-stacktrace-causes, cider--find-last-error-location, cider--goto-expression-start, cider--show-error-buffer-p, cider-new-error-buffer, cider-emit-into-color-buffer, cider-jump-to-compilation-error, cider-find-property.
• Highlight-clearing helpers from the old "Utilities" section (cider--clear-compilation-highlights, cider-clear-compilation-highlights, cider--quit-error-window).
• cider--shorten-error-message (only used as the default of cider-inline-error-message-function).

Coupling:

• cider-eval.el now requires cider-compilation and drops compile from its requires.
• Two consumers that don't go through cider-eval (cider-log.el, cider-test.el) get an explicit require for cider-auto-select-error-buffer.
• The new file forward-declares only cider-repl-mode (used in a derived-mode-p check); no other shims needed.

cider-eval.el: 1650 → 1156 lines. cider-compilation.el: 562 lines (new).

• Compiles clean with `eldev compile --warnings-as-errors`
• All 547 tests pass (`eldev test`)
• No CHANGELOG entry — pure refactor, no user-visible change