Consider replacing httpx with requests for pyodide support

[simontaurus]

Is your feature request related to a problem? Please describe.
Even with wolverdude/GenSON#73 fixed, datamodel-code-generator still depends on httpx, which is not yet supported in pyodide (see koenvo/pyodide-http#37)

Describe the solution you'd like
Replacing httpx with requests would solve this issue.
Beside some mockup patches in the tests, this is merly about two lines:

datamodel-code-generator/datamodel_code_generator/http.py

Line 19 in fcab9a4

return httpx.get(

which can be replaced with

requests.get(url, headers=headers, verify=verify, allow_redirects=follow_redirects, params=params)

and

datamodel-code-generator/datamodel_code_generator/http.py

Line 29 in fcab9a4

return str(httpx.URL(url).join(ref))

which should be replaceable with

urllib.parse.urlparse

wrapped here: https://github.com/encode/httpx/blob/88a81c5d31a4a8b4bd0a860dedd3bb12dc09ff86/httpx/_urls.py#L370

see also https://github.com/search?q=repo%3Akoxudaxi%2Fdatamodel-code-generator%20httpx&type=code

Describe alternatives you've considered
As a temporary workaround, a patch is also possible:

import requests
import httpx
def patch_get(url, headers, verify, follow_redirects, params
    ):
    return requests.get(
        url, headers=headers, verify=verify, allow_redirects=follow_redirects, params=params
    )
httpx.get = patch_get

Additional context
Patch solution is used here: https://oo-ld.github.io/playground-python-yaml/