samples: http_get: move 'not CONFIG_NATIVE_LIBC' filter to POSIX build

[mniestroj]

not CONFIG_NATIVE_LIBC filter is just to prevent building for
native_posix platform with additional options selected by
sample.net.sockets.http_get.posix testcase.

[aescolar]

To the best of my understanding CONFIG_NET_SOCKETS_POSIX_NAMES works with the host libC. So the change is ok.
But, it may be nicer to set CONFIG_PICOLIBC=y in general so we avoid the possible confusion that would follow due to having several symbols with those names around.
We could either do it globally (@rlubos @jukkar would you like this?):

diff --git a/lib/libc/Kconfig b/lib/libc/Kconfig
index 8b71808ff5..e31f04ad33 100644
--- a/lib/libc/Kconfig
+++ b/lib/libc/Kconfig
@@ -61,7 +61,7 @@ menu "C Library"
 
 choice LIBC_IMPLEMENTATION
        prompt "C Library Implementation"
-       default EXTERNAL_LIBC if NATIVE_BUILD && !(NATIVE_LIBRARY && POSIX_API)
+       default EXTERNAL_LIBC if NATIVE_BUILD && !(NATIVE_LIBRARY && (POSIX_API || NET_SOCKETS_POSIX_NAMES))
        default PICOLIBC
        default NEWLIB_LIBC if REQUIRES_FULL_LIBC
        default MINIMAL_LIBC

Or just for this test, (and filter out native_posix, which does not support building with PICO, and is not really adding much anymore):

diff --git a/samples/net/sockets/http_get/sample.yaml b/samples/net/sockets/http_get/sample.yaml
index 999c7ba97d..68a13dac49 100644
--- a/samples/net/sockets/http_get/sample.yaml
+++ b/samples/net/sockets/http_get/sample.yaml
@@ -2,7 +2,12 @@ sample:
   description: BSD Sockets API HTTP GET example
   name: socket_http_get
 common:
-  filter: CONFIG_FULL_LIBC_SUPPORTED and not CONFIG_NATIVE_LIBC
+  filter: CONFIG_FULL_LIBC_SUPPORTED
+  extra_configs:
+    - arch:posix:CONFIG_PICOLIBC=y
+  platform_exclude:
+    - native_posix
+    - native_posix_64
   harness: net
   min_ram: 32
   min_flash: 80

[jukkar]

We could either do it globally (@rlubos @jukkar would you like this?):

I am fine with both, but perhaps the global setting makes more sense if it works properly in all cases.