Adds pre/post boot and node roles

As per kubernetes-sigs/image-builder#894 issue
upstream project opened to use custom Ansible roles pre/post boot of the
node and also pre/post node provisioning.

This opens doors to customize image built for custom requirements, for
example if deployment needs to happen in offline environment that has no
access to the internet and would require to update system with required
changes to look for packages on internal proxies instead.

Also allows to provide extra updates to the system before Kubernetes is
installed along with extra tweaks after.

projects/aws/image-builder/builder/types.go

@@ -77,6 +77,7 @@ type BaremetalConfig struct {
 	IsoConfig
 	RhelConfig
 	ExtraPackagesConfig
+	ExtraOverridesConfig
 }
 
 type CloudstackConfig struct {
@@ -130,3 +131,12 @@ type ExtraPackagesConfig struct {
 	ExtraRepos string `json:"extra_repos,omitempty"`
 	ExtraRpms  string `json:"extra_rpms,omitempty"`
 }
+
+type ExtraOverridesConfig struct {
+	FirstbootCustomRolesPre  string `json:"firstboot_custom_roles_pre,omitempty"`
+	FirstbootCustomRolesPost string `json:"firstboot_custom_roles_post,omitempty"`
+	NodeCustomRolesPre       string `json:"node_custom_roles_pre,omitempty"`
+	NodeCustomRolesPost      string `json:"node_custom_roles_post,omitempty"`
+	DisablePublicRepos       bool   `json:"disable_public_repos,omitempty"`
+	ReenablePublicRepos      bool   `json:"reenable_public_repos,omitempty"`
+}