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/log.lua

@@ -154,7 +154,7 @@ function log.set_level(level)
 end
 
 --- Gets the current log level.
----@return string current log level
+---@return integer current log level
 function log.get_level()
   return current_log_level
 end