OADP-6765: docs: add CA Certificate Bundle documentation for ImageStream backups (#1974)

* docs: add CA Certificate Bundle documentation for ImageStream backups

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: clarify CA certificate handling for ImageStream backups in velero-plugin-for-aws

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: update configuration to include openshift plugin for ImageStream backups

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: enhance clarity and formatting in CA Certificate Bundle documentation for ImageStream backups

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: add detailed component relationship and flow for ImageStream backups

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: clarify the distinction between Velero BSL spec and S3 driver parameters for CA certificate handling

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: clarify distinction between Velero BSL spec and S3 driver parameters for CA certificate handling

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

* docs: enhance documentation on external BSLs for ImageStream backups and CA certificate collection process

Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

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Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>

Author: kaovilai