[browser][icu] Automate custom icu creation

[ilonatommy]

In #80421 and #83585 we enabled loading custom ICU by setting <WasmIcuDataFileName> build property. Customers, in order to create such a custom ICU have to:

1. clone the icu repo,
2. install all the required tools,
3. edit manually the ICU filters,
4. build.

If they use Codespaces they need only steps 3-4 but actually manual edition of filters is the step that is the most error-prone. We would like to make this process easier for them by e.g. creating a dotnet tool.

Tool's input arguments:

• locales - a list of locales that ICU should support,
• outputPath - output path for the resulting ICU.
• target - browser / mobile / wasi

Tool's output:

• *.dat file created in outputPath location.

The tool would create a custom filter based on the locales passed and then trigger the build process.

Future work to be considered:

• integegrate the process with building, e.g. as described in allow stripping the icu data for blazor apps #81552.

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Issue Details

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In #80421 we enabled loading custom ICU by setting <WasmIcuDataFileName> build property. Customers, in order to create such a custom ICU have to:

1. clone the icu repo,
2. install all the required tools,
3. edit manually the ICU filters,
4. build.

If they use Codespaces they need only steps 3-4 but actually manual edition of filters is the step that is the most error-prone. We would like to make this process easier for them by e.g. creating a dotnet tool.

Tool's input arguments:

• locales - a list of locales that ICU should support,
• outputPath - output path for the resulting ICU.
• target - browser / mobile / wasi

Tool's output:

• *.dat file created in outputPath location.

The tool would create a custom filter based on the locales passed and then trigger the build process.

Author:	ilonatommy
Assignees:	directhex, steveisok, ilonatommy
Labels:	arch-wasm, packaging
Milestone:	-