Add bigboot role

Copy the bigboot role (along with initramfs) as is from its separate repo
Apart from some Jinja formatting only the README and changelog file were added or changed

Signed-off-by: Ygal Blum <ygal.blum@gmail.com>

README.md

@@ -11,6 +11,8 @@ A reliable snapshot/rollback capability is a key feature required to enable the
 These are the roles included in the collection. Follow the links below to see the detailed documentation and example playbooks for each role.
 
 - [`lvm_snapshots`](./roles/lvm_snapshots/) - controls creation and rollback for a defined set of LVM snapshot volumes
+- [`bigboot`](./roles/bigboot/) - controls increasing of the boot partition while moving, and shrinking if needed, the adjacent partition
+- [`initramfs`](./roles/initramfs/) - controls the atomic flow of building and using a temporary initramfs in a reboot and restoring the original one
 
 Additional roles are planned to support shrinking logical volumes to make free space available in a volume group and relocating physical volumes to enable increasing the size of a /boot /partition.
 

changelogs/fragments/add-bigboot-role.yml

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+major_changes:
+  - New role, initramfs, to execute an atomic flow of building and using a temporary initramfs in a reboot and restoring the original one
+  - New role, bigboot, to increase the boot partition while moving, and shrinking if needed, the adjacent partition

roles/bigboot/README.md

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+# bigboot
+
+The `bigboot` role is used to increase boot partition.
+
+The role is designed to support the automation of RHEL in-place upgrades, but can also be used for other purposes.
+
+## Contents
+
+The role contains the shell scripts to increase the size of the boot partition, as well as the script wrapping it to run as part of the pre-mount step during the boot process.
+Finally, there is a copy of the [`sfdisk`](https://man7.org/linux/man-pages/man8/sfdisk.8.html) binary with version `2.38.1` to ensure the extend script will work regardless of the `util-linux` package installed in the target host.
+
+## Role Variables
+
+### `bigboot_size`
+
+The variable `bigboot_size` sets the target size of the boot partition after the role has completed.
+The value can be either in bytes or with optional single letter suffix (1024 bases).
+See `Unit options` type `iec` of [`numfmt`](https://man7.org/linux/man-pages/man1/numfmt.1.html)
+
+
+## Example of a playbook to run the role
+The following yaml is an example of a playbook that runs the role against a group of hosts named `rhel` and increasing the size of its boot partition by 1G.
+The boot partition is automatically retrieved by the role by identifying the existing mounted partition to `/boot` and passing the information to the script using the `kernel_opts`.
+
+```yaml
+- name: Extend boot partition playbook
+  hosts: all
+  vars:
+    bigboot_size: 1G
+  roles:
+    - bigboot
+```
+
+# Validate execution
+The script will add an entry to the kernel messages (`/dev/kmsg`) with success or failure and the time it took to process.
+In case of failure, it may also include an error message retrieved from the execution of the script.
+
+A successful execution will look similar to this:
+```bash
+[root@localhost ~]# dmesg |grep pre-mount
+[  357.163522] [dracut-pre-mount] Boot partition /dev/vda1 successfully increased by 1G (356 seconds)
+```

roles/bigboot/defaults/main.yaml

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+bigboot_size: