fuchsia: wire `tzdata-icu` capability through

[filmil]

Is there an existing issue for this?

• I have searched the existing issues
• I have read the guide to filing a bug

Use case

Fuchsia is dismantling the config-data mechanism which was used in the past to deliver this information. Time zone
data used to be deployed as part of config-data, but we are moving towards a separate directory capability.

We should modify the CML files in use in Flutter to use this new capability.

Proposal

Please assign to me, I will work on it.