fix(lsp): lint warnings, default offset_encoding #24046

- fix lint / analysis warnings
- locations_to_items(): get default offset_encoding from active client
- character_offset(): get default offset_encoding from active client

runtime/lua/vim/lsp/buf.lua

@@ -581,9 +581,9 @@ function M.document_highlight()
 end
 
 --- Removes document highlights from current buffer.
----
-function M.clear_references()
-  util.buf_clear_references()
+--- @param bufnr integer|nil
+function M.clear_references(bufnr)
+  util.buf_clear_references(bufnr or 0)
 end
 
 ---@private