Branched off from #998 -- creating this issue to cover the remaining paste-related lints mentioned there that aren't making the 3.0.0 cut

• Upstreaming linters from Google's internal linting suite #884 PasteFilePathLinter: paste(sep = "/") ➡️ file.path()
• Upstreaming linters from Google's internal linting suite #884 PasteStrrepLinter: paste(rep(), collapse="") ➡️ strrep() extend paste_linter() for strrep() equivalents #1652
• paste0(x, collapse = ) ➡️ paste(x, collapse = )