webrepl: support access from LAN, without internet

Host everything on the device itself, rather than redirecting
to https://micropython.org/webrepl/ because that doesn't work when
there is not internet, including when the device is in Access Point
mode.

This was a bit slow, because of the many files and being pretty large,
but the inline_minify_webrepl.py makes this much better and brings it
down to around 1s to load the page, versus 20 seconds.

The minification also reduces the size from around 160KB to 80KB.

.gitignore

@@ -28,8 +28,11 @@ __pycache__/
 *$py.class
 *.so
 
-# these get created:
+# these get created by the build system, don't know why:
 c_mpos/c_mpos
 
 # build files
 *.bin
+
+# auto created by inline_minify_webrepl.py
+internal_filesystem/builtin/html/webrepl_inlined_minified.html