OpenSSH 7.7p1, Unicode 11.0.0, and bug fixes

• Update to libdot 1.22. Unicode 11.0.0 updates and new helpers.
• Update to hterm 1.79. A11y (screen reader) improvements & keyboard/mouse fixes.
• crosh: Extend for arbitrary commands.
• crosh: Support passing command line args down.
• sftp: Fix directory deletion and copying.
• docs: Improve building/reference documentation.
• extension: Add a link to the options page at the bottom.
• Use new lib.f.lastError helper.
• crosh: Display errors from terminalPrivate if available.
• removeFile: Fix param typo.
• docs: Update the hex ids info.
• terminal: Adds the crostini terminal icon to use with crosh.
• ssh_client: Update to openssh-7.7p1.
• FAQ: Add a X11 forwarding answer.
• FAQ: Add omnibox with multiple extensions.
• API: Add onSendMessageExternal to allow FilesApp to sftp mount.
• lint: Clean up semi-colon usage.
• a11y: Add basic support for announcing command output to AT.
• Handle option page loading failures.
• docs: Document the crosh code on the Chrome side.
• gsc: Implement a PIN cache for GSC agent.
• a11y: Preserve selection when scrolling collapsed selections.
• crosh: Pass the selected profile over.
• ssh_client: Stub out permission check.
• agent: Improve gnubby extension probing.
• Crush all images.
• release: Automatically minimize translations.
• ssh_client: Add a echosshd utility.
• l10n: Improve pref descriptions and translation tips.
• l10n: Import updated translations.
• prefs: Auto-select icon for preferences page.