fish: command substitution chokes on '-- \' in multi-line command

[ph03]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.80.0
• OS Version: ubuntu 22.04

Steps to Reproduce:

1. Start a fish shell in integrated terminal.
2. Issue multi-line command with -- \ in one of the lines, e.g.

   $ echo \
      -- \
      test
   

3. Results in error

string join: Unknown option “-- \\”

~/.vscode-server/bin/660393deaaa6d1996740ff4880f1bad43768c814/out/vs/workbench/contrib/terminal/browser/media/fish_xdg_data/fish/vendor_conf.d/shellIntegration.fish (line 1): 
string join ";" $argv
^
in command substitution
        called on line 65 of file ~/.vscode-server/bin/660393deaaa6d1996740ff4880f1bad43768c814/out/vs/workbench/contrib/terminal/browser/media/fish_xdg_data/fish/vendor_conf.d/shellIntegration.fish
in function '__vsc_esc' with arguments 'E echo\ \\\\ --\ \\\\ test'
        called on line 72 of file ~/.vscode-server/bin/660393deaaa6d1996740ff4880f1bad43768c814/out/vs/workbench/contrib/terminal/browser/media/fish_xdg_data/fish/vendor_conf.d/shellIntegration.fish
in function '__vsc_cmd_executed' with arguments 'echo\ \\\n--\ \\\ntest'
in event handler: handler for generic event “fish_preexec”

(Type 'help string' for related documentation)

Issue started with vscode-1.80.0