bitbake: fetch2/wget: Canonicalize DL_DIR paths for wget2 compatibility

Some distributions (namely Fedora Core 40) have started replacing
wget with wget2. There are some changes to wget2 that make it
incompatible with wget:

1. ftp/ftps is not supported anymore
2. progress 'dot' is not yet supported
3. Relative paths in -P and -O are not correctly dealt with

Item 1: Is already dealt with since Scarthgap by only adding the
option --passive-ftp when the URL specifies ftp/sftp. While that
won't help if ftp/sftp is actually required it at least does
not break http/https downloads.

Item 2: While not supported it at least does not break the operation.

Item 3: If there are relative path components in -P or -O then wget2
only deals with them correctly if there is one, and only one, relative
path component at the beginning of the path:

-P ./downloads     works
-P ../downloads    works
-P ../../downloads does not work
-P ./../downloads  does not work
-P /home/user/downloads/../downloads does not work

In cases where there are more than one relative path component at
the beginning of the path and/or one or more reltaive path
component somewhere in the middle or end of the path, wget2 aborts
with the message Internal error: Unexpected relative path: '<path>')

Such can happen if DL_DIR includes relative path components e.g.
DL_DIR = "${TOPDIR}/../../downloads".

This patch canonicalizes DL_DIR before it is passed to wget.

(Bitbake rev: 07081a94997142746f7d345c27bc6805231d025d)

Signed-off-by: Rudolf J Streif <rudolf.streif@ibeeto.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 3e4208952b086adc510e78c1c5f9cf4550d79dc9)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
(cherry picked from commit 47678142e26bb76d1351886060deff5e75039bc9)
Signed-off-by: Steve Sakoman <steve@sakoman.com>