Capslock on host causes Hyper-V provisioning to fail

_This issue was originally opened by @voltagex in https://github.com/hashicorp/packer/issues/11793 and has been migrated to this repository. The original issue description is below._

---

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#### Overview of the Issue

If capslock is on on the host, the wrong characters are sent to Hyper-V.

A paragraph or two about the issue you're experiencing.

#### Reproduction Steps

```
#hit capslock
packer build my_file.pkr.hcl
```

### Packer version

From `packer version`

### Simplified Packer Template
```hcl
source "hyperv-iso" "autogenerated_1" {
boot_wait = "1s"
boot_command = [
"",
"set gfxpayload=keep",
"linux /casper/vmlinuz ",
"debug autoinstall 'ds=nocloud-net;s=http://10.0.0.144:8000/' --- ",
"noprompt autoinstall 'ds=nocloud-net;s=http://10.0.0.144:8000/' --- ",
"initrd /casper/initrd",
"boot"]

communicator = "ssh"
cpus = "4"
disk_size = "20000"
enable_secure_boot = false
generation = 2
guest_additions_mode = "disable"
http_directory = "./local-testing/"
iso_checksum = "file:https://mirror.aarnet.edu.au/pub/ubuntu/releases/20.04.4/SHA256SUMS"
iso_url = "http://mirror.aarnet.edu.au/pub/ubuntu/releases/20.04.4/ubuntu-20.04.4-live-server-amd64.iso"
#iso_checksum = "file:https://mirror.aarnet.edu.au/pub/ubuntu/releases/22.04/SHA256SUMS"
#iso_url = "http://mirror.aarnet.edu.au/pub/ubuntu/releases/22.04/ubuntu-22.04-live-server-amd64.iso"
memory = "4096"
shutdown_command = "echo 'packer' | sudo -S -E shutdown -P now"
ssh_password = "packer"
ssh_timeout = "4h"
ssh_username = "packer"
vm_name = "${var.vm_name}"
}

build {
sources = ["source.hyperv-iso.autogenerated_1"]
}
```

### Operating system and Environment details

Windows 11, Packer 1.7.8 (because 1.8.0 fails with another bug I'm about to raise)