Fix HTTP server buffer

[vinc]

Sometimes a call to socket.recv() doesn't return the whole receive buffer and some HTTP requests are not correctly parsed. This PR fixes this issue by rebuilding the whole buffer before parsing the request. It also fixes how the server join its root directory and the request path.

[vinc]

This PR is used to test the e1000 driver in #337 on real hardware.

[vinc]

Here's a test of various possibilities regarding the server directory and the request path:

~
> dhcp
ip:  10.0.2.15/24
gw:  10.0.2.2
dns: 10.0.2.3

~
> httpd
HTTP Server listening on 0.0.0.0:80
10.0.2.2 - - [2024-04-03 10:12:25 +0000] "GET /" 200 297
^C

~
> httpd -d /
HTTP Server listening on 0.0.0.0:80
10.0.2.2 - - [2024-04-03 10:12:34 +0000] "GET /" 200 309
10.0.2.2 - - [2024-04-03 10:12:38 +0000] "GET /tmp" 301 28
10.0.2.2 - - [2024-04-03 10:12:39 +0000] "GET /tmp/" 200 383
^C

~
> httpd -d /tmp
HTTP Server listening on 0.0.0.0:80
10.0.2.2 - - [2024-04-03 10:12:47 +0000] "GET /" 200 347
10.0.2.2 - - [2024-04-03 10:12:50 +0000] "GET /lisp" 301 28
10.0.2.2 - - [2024-04-03 10:12:51 +0000] "GET /lisp/" 200 377
^C

~
> httpd -d /tmp/
HTTP Server listening on 0.0.0.0:80
10.0.2.2 - - [2024-04-03 10:12:57 +0000] "GET /" 200 347
10.0.2.2 - - [2024-04-03 10:13:01 +0000] "GET /lisp" 301 28
10.0.2.2 - - [2024-04-03 10:13:02 +0000] "GET /lisp/" 200 377
^C

~
> /tmp

/tmp
> httpd
HTTP Server listening on 0.0.0.0:80
10.0.2.2 - - [2024-04-03 10:13:31 +0000] "GET /" 200 347
10.0.2.2 - - [2024-04-03 10:13:33 +0000] "GET /lisp" 301 28
10.0.2.2 - - [2024-04-03 10:13:34 +0000] "GET /lisp/" 200 377
^C

[vinc]

This commit takes care of this case:

/
> httpd -d tmp
HTTP Server listening on 0.0.0.0:80
10.0.2.2 - - [2024-04-03 15:01:21 +0000] "GET /" 200 347
10.0.2.2 - - [2024-04-03 15:01:24 +0000] "GET /lisp" 301 28
10.0.2.2 - - [2024-04-03 15:01:26 +0000] "GET /lisp/" 200 377
^C

And it moves the trim on the root directory outside of the function to be done only once during startup to optimize it.