bug: improve the comment Id code structure

bug/comment.go

bug/comment_test.go

bug/op_add_comment.go

bug/op_create.go

bug/snapshot.go

cache/repo_cache_bug.go

commands/comment_edit.go

commands/select/select.go

doc/man/git-bug-comment-edit.1

doc/man/git-bug-comment.1

doc/md/git-bug_comment.md

doc/md/git-bug_comment_edit.md

misc/bash_completion/git-bug

misc/powershell_completion/git-bug

misc/zsh_completion/git-bug