Description of problem:

Specifying a proxy to fetch Stage2 was working fine with RHEL8, e.g.:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
url --url=http://localhost/rhel91 --proxy=http://192.168.122.1:3128
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Such stanza doesn't work on RHEL9 anymore, we get the following on boot:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
[   16.790278] dracut-initqueue[1181]: ////lib/url-lib.sh@77(curl_fetch_url): curl --globoff --location --retry 3 --retry-connrefused --fail --show-error --remote-name http://localhost/rhel91/images/install.img
[   16.790596] dracut-initqueue[1182]:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
[   16.790629] dracut-initqueue[1182]:                                  Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
[   16.790680] dracut-initqueue[1182]: curl: (7) Failed to connect to localhost port 80: Connection refused
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Here above we can see `curl` didn't execute with `--proxy` argument.
The root cause for this is `curl` command, built by `lib/url-lib.sh` snippet below, relies on "proxy=" command-line variable:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
 59 curl_args="--globoff --location --retry 3 --fail --show-error"
 60 getargbool 0 rd.noverifyssl && curl_args="$curl_args --insecure"
 61 
 62 proxy=$(getarg proxy=)
 63 [ -n "$proxy" ] && curl_args="$curl_args --proxy $proxy"
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Unfortunately, there is no such `proxy=` variable anymore, since with commit **b88e10fe3029602b369c719506588097fcbdf80b**, `parse-kickstart` now generates a `inst.proxy=` variable instead:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
--- a/dracut/parse-kickstart
+++ b/dracut/parse-kickstart
@@ -157,7 +157,7 @@ class DracutURL(Url, DracutArgsMixin):
         if self.noverifyssl:
             args.append("rd.noverifyssl")
         if self.proxy:
-            args.append("proxy=%s" % self.proxy)
+            args.append("inst.proxy=%s" % self.proxy)
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

We can confirm the generated cmdline snippet:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
# cat /etc/cmdline.d/80-kickstart.conf 
inst.text
ip=enp1s0:dhcp: bootdev=enp1s0
inst.repo=http://localhost/rhel91
inst.proxy=http://192.168.122.1:3128
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

On RHEL8, it was:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
# cat /etc/cmdline.d/80-kickstart.conf 
inst.text
ip=enp1s0:dhcp: bootdev=enp1s0
inst.repo=http://localhost/rhel91
proxy=http://192.168.122.1:3128
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

If new variable (`inst.proxy`) is expected, then lib/url-lib.sh must search for `inst.proxy` as well, but this file is shipped with *dracut*, not *dracut-anaconda*, so this would become inconsistent.

Version-Release number of selected component (if applicable):

RHEL9.0+ DVD

How reproducible:

Always

Steps to Reproduce:
1. Boot a VM with RHEL9 kernel and initramfs and kickstart containing a URL with a proxy

Actual results:

Can't load Stage2

Expected results:

Can load Stage2