[FIX] core: reset current_thread.dbname/uid between requests

In [HTTPocalypse] the `odoo/service/wsgi_server.py` file has been
removed and its features has been spread to other files. One of the
feature was reseting those few thread-local variables[^1] before
processing any new request:

    if hasattr(threading.current_thread(), 'uid'):
        del threading.current_thread().uid
    if hasattr(threading.current_thread(), 'dbname'):
        del threading.current_thread().dbname
    if hasattr(threading.current_thread(), 'url'):
        del threading.current_thread().url

In [HTTPocalypse] the `url`[^2] is correctly set at its definitive value
at the beginning of the request so there is no need to delete it before
processing.

On the other hand, `dbname`[^3][^4] and `uid`[^5] are only set when the
request is processed by `_serve_db`, i.e. that the user is connected to
a database already. Those values weren't reset at the begining of the
next request so in case that next request was processed by `_serve_nodb`
or `_serve_static`, the dbname and uid of the previous request would
still be present.

This commit restores both `del uid` and `del dbname` at the beginning of
the http stack, before the request is processed.

[HTTPocalypse]: odoo/odoo#78857
[^1]: https://github.com/odoo/odoo/blob/a1361d6629a829fd622f2a1a1b3e5b025050eaf9/odoo/service/wsgi_server.py#L80-L85
[^2]: https://github.com/odoo/odoo/blob/0e629cd2a1fc3623b579a38ae534fbdfae9b38a3/odoo/http.py#L1987
[^3]: https://github.com/odoo/odoo/blob/0e629cd2a1fc3623b579a38ae534fbdfae9b38a3/odoo/http.py#L1563
[^4]: https://github.com/odoo/odoo/blob/0e629cd2a1fc3623b579a38ae534fbdfae9b38a3/odoo/modules/registry.py#L70
[^5]: https://github.com/odoo/odoo/blob/0e629cd2a1fc3623b579a38ae534fbdfae9b38a3/odoo/http.py#L1582

closes odoo/odoo#125205

X-original-commit: c327c4586243430751100c8980169ae067383b1c
Signed-off-by: Julien Castiaux (juc) <juc@odoo.com>

odoo/http.py

@@ -2102,6 +2102,10 @@ class Application:
         current_thread.query_count = 0
         current_thread.query_time = 0
         current_thread.perf_t0 = time.time()
+        if hasattr(current_thread, 'dbname'):
+            del current_thread.dbname
+        if hasattr(current_thread, 'uid'):
+            del current_thread.uid
 
         if odoo.tools.config['proxy_mode'] and environ.get("HTTP_X_FORWARDED_HOST"):
             # The ProxyFix middleware has a side effect of updating the