Refactor eldoc (#448)
* Refactor eldoc
* Rename lsp-symbol-highlight to lsp-document-highlight
We should keep consistency with LSP names
* Delete lsp-enable-codeaction
It does not make sense to update codeAction again and again in eldoc
They can add it to lsp-eldoc-hook if they really want the feature
* Delete lsp-hover-text-function, lsp-enable-eldoc, lsp-highlight-symbol-at-point in favor of lsp-eldoc-hooks
lsp-ui-doc users are not affected.
* Add defcustom lsp-eldoc-hook to customize requests to send (default: documentHighlight, hover)
* Use add-function instead of setq to set eldoc-documentation-function
* Bump to 5.0
