feat(LSP): Regroup modules and settings in Vim's module

Keeping the same semantics, reordered all the module loading inside the
Neovim's LSP client configuration module.

nvim/lsp_client_settings.vim

@@ -1,13 +1,3 @@
-lua << EOF
-require("lsp.diagnostics")
-EOF
-
-set completeopt=menuone,noinsert,noselect
-
-lua << EOF
-require("lsp.keymaps")
-EOF
-
 " nvim-lspconfig
 lua << EOF
 -- This section must be before setting up any LSP server for the automatic
@@ -28,7 +18,9 @@ for _, lsp in ipairs(servers) do
 end
 EOF
 
-" nvim-cmp
+set completeopt=menuone,noinsert,noselect
 lua << EOF
+require("lsp.keymaps")
 require("lsp.completion")
+require("lsp.diagnostics")
 EOF