fix: prevent panic when dumping structs with promoted fields

[Akkadius]

Summary:

• Fixes a panic: reflect: Field index out of bounds when dumping structs that embed other structs (i.e. promoted fields).
• Replaces incorrect use of t.Field(i) with reflect.VisibleFields(t) + FieldByIndex, which safely handles embedded/promoted fields.

Before:

for i := range reflect.VisibleFields(t) {
    field := t.Field(i) // ❌ may panic

After:

for _, field := range reflect.VisibleFields(t) {
    fieldVal := v.FieldByIndex(field.Index) // ✅ safe

Test added:
✅ TestPanicOnVisibleFieldsIndexMismatch — reproduces panic with embedded struct and confirms resolution.

Test Before

=== RUN   TestPanicOnVisibleFieldsIndexMismatch
--- FAIL: TestPanicOnVisibleFieldsIndexMismatch (0.00s)
panic: reflect: Field index out of bounds [recovered]
	panic: reflect: Field index out of bounds

goroutine 35 [running]:
testing.tRunner.func1.2({0x100b11d40, 0x100b59130})
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/testing/testing.go:1632 +0x1bc
testing.tRunner.func1()
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/testing/testing.go:1635 +0x334
panic({0x100b11d40?, 0x100b59130?})
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/runtime/panic.go:785 +0x124
reflect.(*structType).Field(0x1479499f8?, 0x0?)
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/reflect/type.go:1116 +0x164
reflect.(*rtype).Field(0x100b59e38?, 0x14000144210?)
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/reflect/type.go:749 +0x50
github.com/goforj/godump.printValue(0x14000144210, {0x100b2d0e0?, 0x140001401e0?, 0x10090831c?}, 0x0, 0x14000175e78)
	/Users/cmiles/code/godump/godump.go:220 +0x1038
github.com/goforj/godump.writeDump(0x14000144210, {0x1400011af48, 0x1, 0x1400011af08?})
	/Users/cmiles/code/godump/godump.go:168 +0xc4
github.com/goforj/godump.DumpStr({0x1400011af48, 0x1, 0x1})
	/Users/cmiles/code/godump/godump.go:83 +0x94
github.com/goforj/godump.TestPanicOnVisibleFieldsIndexMismatch(0x14000134820?)
	/Users/cmiles/code/godump/godump_test.go:502 +0x68
testing.tRunner(0x14000134820, 0x100b57b98)
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/testing/testing.go:1690 +0xe4
created by testing.(*T).Run in goroutine 1
	/Users/cmiles/go/pkg/mod/golang.org/[email protected]/src/testing/testing.go:1743 +0x314

Test After

=== RUN   TestPanicOnVisibleFieldsIndexMismatch
--- PASS: TestPanicOnVisibleFieldsIndexMismatch (0.00s)
PASS

Process finished with the exit code 0