[WIP] Add ICU support in embedded v8.

[kishiguro]

This is PR for denoland/deno#1968 Add ICU support in embedded v8. Please note this PR is still work in progress. Following changes are made in this PR.

• Add submodule third_part/icu@ f222396
• Set v8_enable_i18n_support = true in .gn for ICU support.

We need have following change to submodule icu.

• Set icu_use_data_file = false in third_party/icu/config.gni
• (Mac build fix) third_party/icu/config/mac/BUILD.gn b/config/mac/BUILD.gn
• (Windows build fix) third_party/icu/scripts/make_data_assembly.py

Would you mind to suggest how I should modify submodule code with current build ecosystem? Apply patch from build.rs or fork the original repository and apply the patch to it?

[CLAassistant]

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[piscisaureus]

We'll have to find a solution to make the crate stay under 10 MB (the limit imposed by crates.io).
ICU data might have to live in a separate crate or get downloaded through some other means.

[kishiguro]

I see. Maybe it is better to download each platform's *.{o, obj} file which has ICU data.

[kishiguro]

I've made updated PR at #390. So let me close this ticket.