Hostname changing causes unexpected issues.

**Describe the bug**
Toolbox fails to resolve names together with systemd-resolved. Filled systemd issue https://github.com/systemd/systemd/issues/33870, but systemd maintainers think hostname should not be changed. And that it is failure of toolbox to change system identification, but not fully.

Initially reported at bug https://bugzilla.redhat.com/show_bug.cgi?id=2291062

Is the changing of hostname good idea, when variable ``$HOSTNAME`` stays unmodified? Is there specific reason, why it is implemented the current way? Would not some shell variable work better maybe just overriding PS1 prompt?

**Steps how to reproduce the behaviour**
1. Have Fedora 40
2. Spawn Fedora 40 toolbox by `toolbox enter`.
3. Have dns-suffix on your connection (*lan* for example).
4. Try to resolve ``toolbox.lan``, where ``toolbox`` is what ``$(hostname)`` command returns.

**Expected behaviour**
It should resolve fast and clean. It should not fail to take a long to resolve.

**Actual behaviour**
Under specific conditions, because NSS plugin ``resolve`` is ordered *before* ``myhostname`` plugin, it may take quite a long time. That is because unlike ``myhostname`` plugin, ``systemd-resolved.service`` does not understand that toolbox.$SUFFIX is its own hostname. Tries it to find on the network and may fail when doing that.

**Screenshots**
None, see https://bugzilla.redhat.com/show_bug.cgi?id=2291062

**Output of `toolbox --version` (v0.0.90+)**
0.0.99.5

**Toolbx package info (`rpm -q toolbox`)**
`toolbox-0.0.99.5-11.fc40.x86_64`

**Output of `podman version`**
```
# podman version
Client: Podman Engine
Version: 5.2.1
API Version: 5.2.1
Go Version: go1.22.5
Built: Tue Aug 13 20:00:00 2024
OS/Arch: linux/amd64
```

**Podman package info (`rpm -q podman`)**
`podman-5.2.1-1.fc40.x86_64`

**Info about your OS**
Fedora 40

**Additional context**

This happens because some black magic is specially applied on $HOSTNAME queries. But because toolbox uses different hostname, it does not recognize it as own name at systemd-resolved and resolves it like any other name. On certainly broken networks that may take exceptionally long time.

This happens on Fedora 40, where just ``toolbox enter`` is used and systemd-resolved is enabled by default.

```
# grep hosts /etc/nsswitch.conf
hosts: files resolve [!UNAVAIL=return] myhostname dns
```