[iOS/GN] Port ios/chrome/tools/strings/generate_localizable_strings.gyp to GN.
[iOS/GN] Port ios/chrome/tools/strings/generate_localizable_strings.gyp to GN.

BUG=459705

Review URL: https://codereview.chromium.org/1913063002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#389060}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk