Remove `isXXXXX` and provide only `is.XXXXX`

[lambdalisue]

Taking into account the potential for future advancements in Deno runtime, including tree shaking support, and various other factors, we initially exposed functions of the isXXXXX type. However, with the requirement for cross-platform functionality driven by JSR support, the feasibility of tree shaking has been reduced. Offering the same function in two manners only adds to complexity and confusion in this context, leading us to opt for its removal.

This action mitigates the risk of unintended exposure of functions or types through export * from "...". Furthermore, it allows us to eliminate tests aimed at verifying if is encompasses all exposed isXXXXX functions.