Run FreeRTOS and heap checking for datetime, temperature, and simple casemap, and triage issues

[sffc]

A Google 1st party product has i18n needs including date and time formatting, temperature, day of week, and simple case map (more details here). They run in a resource-constrained environment. We should run these code paths through the framework we currently use for testing FixedDecimalFormatter and triage any issues we find. We'd like the core code paths to be alloc-free and no memory.

[zbraniecki]

Are we competing with existing solution or trying to propose a solution within a budget?

[sffc]

We're competing against a narrow home-grown solution that was written before ICU4X in a time when ICU4C was too big to fit in the resource constrained environment.