@embroider/macros isDevelopingApp should be available in runtime (consistent with isTesting)

[rtablada]

When using @embroider/macros any use of isTesting used outside of a macroCondition will be built and rewritten to use an import from @embroider/macros/runtime. However, isDevelopingApp does not follow this behavior and was quite confusing when it would suddenly show up as an undeclared variable in our app code.

Since the two methods are described together in documentation, I think it would make sense to have similar runtime availability.

[ef4]

isTesting has a runtime implementation because it can actually be changed at runtime (the test suite sets it to true). isDevelopingApp cannot be changed at runtime.

However, isDevelopingApp does not follow this behavior and was quite confusing when it would suddenly show up as an undeclared variable in our app code.

This sounds like a bug. It should never be an undeclared variable.