Backmerge: #1822 Fasta: All Peptides should be saved to FASTA format and (use N/X symbol as well)

[even1024]

Backmerge request

• [ ] PR name follows the pattern Backmerge: #1234 – issue name
• [ ] PR is linked with the issue
• [ ] base branch (master or release/xx) is correct
• [ ] code contains only backmerge changes