Allow to use hostname in TinkerbellTemplateConfig templating

**What would you like to be added**:
We have the need to modify the default netplan config for Bare Metal (ubuntu), to be able to use bonding configuration with static IP assignment (we have 2 bonds, one for storage one for data traffic). We generated the `TinkerbellTemplateConfig` with `eksctl anywhere generate tinkerbelltemplateconfig -f cluster.yaml` and noticed that some templating can be used for the actions:
```
DEST_DISK: '{{ index .Hardware.Disks 0 }}'
```

Our plan is to fetch the netplan files from the admin host using curl (using a cexec action). As we need a per host based netplan, it would be nice to include the hostname in the URL through a template like the following (see CMD_LINE):
```
- environment:
BLOCK_DEVICE: '{{ formatPartition ( index .Hardware.Disks 0 ) 2 }}'
CHROOT: "y"
CMD_LINE: curl --output /etc/netplan/config.yaml http://ip.of.admin.host:8080/netplan/{{ .Hardware.Hostname }}.yaml && chown 0:0 /etc/netplan/config.yaml && chmod 0644 /etc/netplan/config.yaml
DEFAULT_INTERPRETER: /bin/sh -c
FS_TYPE: ext4
image: public.ecr.aws/eks-anywhere/tinkerbell/hub/cexec:404dab73a8a7f33e973c6e71782f07e82b125da9-eks-a-58
name: fetch-netplan-from-admin-host
timeout: 90
```

Unfortunately, we could not find any documentation about this templating. However from the upstream code, it seems, only disks are added to the `.Hardware` at the moment: https://github.com/tinkerbell/tink/blob/v0.10.0/internal/workflow/reconciler.go#L134

Is this findings correct? Would it be possible to extend this struct with more information like `hostname` so, we can use it in TinkerbellTemplateConfig actions?

**Why is this needed**:
Currently, we have very limited possibilities in TinkerbellTemplateConfig when it comes to a per host property that is not exposed in any way (like an IP address of a storage bond interface). Basically, this forces us to define a TinkerbellTemplateConfig per host. If the templating could be extended with per host based variables (like hostname) then, a single TinkerbellTemplateConfig could be used for many real life use cases.

Start with the upstream internal/workflow/reconciler.go entry point linked in the issue and review how the Hardware template data is populated. Trace the TinkerbellTemplateConfig generation path and its existing documentation before deciding where hostname support belongs. Done means a single template can use each host's hostname in an action, with the supported variable documented.

Written by the indexing model from the issue text.