fix: [#300] proper fix for clippy large_stack_arrays using builder pattern

The vec![] macro creates a temporary stack array [T; N] before moving
to heap. For large structs like ServiceTopology (~56 bytes), this can
exceed clippy's 16KB threshold when multiple items are created.

Solution: Added ServiceTopologyVecBuilder that uses Vec::with_capacity()
+ push() to allocate directly on heap, avoiding the stack array entirely.

This re-enables all 22 tests that were temporarily commented out.

See: rust-lang/rust-clippy#12586

Author: josecelano