feat: add ollama as supported provider (#1543)

* feat: add ollama as supported provider

*This implementation is only working with `stream = true`*
- Uses the actual ollama api and allows for passing additional options
- Properly passes the system prompt to api

Use ollama as provider in opts like this:
opts = {
        debug = true,
        provider = "ollama",
        ollama = {
                api_key_name = "",
                endpoint = "http://127.0.0.1:11434",
                model = "qwen2.5-coder:latest",
                options = {
                        num_ctx = 32768,
                        temperature = 0,
                },
                stream = true,
        },

* fix: ollama types

---------

Co-authored-by: jtabke <25010496+jtabke@users.noreply.github.com>

lua/avante/providers/init.lua

@@ -18,6 +18,7 @@ local DressingState = { winid = nil, input_winid = nil, input_bufnr = nil }
 ---@field gemini AvanteProviderFunctor
 ---@field cohere AvanteProviderFunctor
 ---@field bedrock AvanteBedrockProviderFunctor
+---@field ollama AvanteProviderFunctor
 local M = {}
 
 ---@class EnvironmentHandler
@@ -152,8 +153,13 @@ M = setmetatable(M, {
   __index = function(t, k)
     local provider_config = M.get_config(k)
 
+    if Config.vendors[k] ~= nil and k == "ollama" then
+      Utils.warn(
+        "ollama is now a first-class provider in avante.nvim, please stop using vendors to define ollama, for migration guide please refer to: https://github.com/yetone/avante.nvim/wiki/Custom-providers#ollama"
+      )
+    end
     ---@diagnostic disable: undefined-field,no-unknown,inject-field
-    if Config.vendors[k] ~= nil then
+    if Config.vendors[k] ~= nil and k ~= "ollama" then
       if provider_config.parse_response_data ~= nil then
         Utils.error("parse_response_data is not supported for avante.nvim vendors")
       end