unable to add partition in tinkerbell action

**What happened**:

I'm creating a EKS anywhere cluster for bare metal

After the action "stream-image" (the image is ubuntu 20.04 EFI), fdisk shows 2 partitions, /dev/sda1 and /dev/sda2 (total disk size is 6G, while the actual disk size is around 480G).

I create a new action to add a new partition with such command:
printf "n\np\n3\n\n+10G\nw" | fdisk /dev/sda

However, I don't see the new partition created (even right within my new action)

Do you know why?

**What you expected to happen**: I expect the cluster creation will succeeds and the node has 3 partitions instead of 2.

**How to reproduce it (as minimally and precisely as possible)**: mentioned above

**Anything else we need to know?**:

**Environment**:
- EKS Anywhere Release: v0.18.2
- EKS Distro Release: 1.28

Start by reproducing the bare-metal cluster setup in EKS Anywhere v0.18.2, focusing on the "stream-image" action and the following custom action that runs fdisk on /dev/sda. Check the partition layout before and after the action and determine why the requested third partition is not visible. Done means the cause is documented and cluster creation produces the expected three partitions.

Written by the indexing model from the issue text.