Add LLM for ChatGLM(2)-6B API (#7774)

Description:
Add LLM for ChatGLM-6B & ChatGLM2-6B API

Related Issue: 
Will the langchain support ChatGLM? #4766
Add support for selfhost models like ChatGLM or transformer models #1780

Dependencies: 
No extra library install required. 
It wraps api call to a ChatGLM(2)-6B server(start with api.py), so api
endpoint is required to run.

Tag maintainer:  @mlot 

Any comments on this PR would be appreciated.
---------

Co-authored-by: mlot <limpo2000@gmail.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

tests/integration_tests/llms/test_chatglm.py

@@ -0,0 +1,18 @@
+"""Test ChatGLM API wrapper."""
+from langchain.llms.chatglm import ChatGLM
+from langchain.schema import LLMResult
+
+
+def test_chatglm_call() -> None:
+    """Test valid call to chatglm."""
+    llm = ChatGLM()
+    output = llm("北京和上海这两座城市有什么不同？")
+    assert isinstance(output, str)
+
+
+def test_chatglm_generate() -> None:
+    """Test valid call to chatglm."""
+    llm = ChatGLM()
+    output = llm.generate(["who are you"])
+    assert isinstance(output, LLMResult)
+    assert isinstance(output.generations, list)