configstruct: fix parsing of invalid booleans in the config

Apparently fmt.Sscanln doesn't parse bool's properly and this isn't
likely to be fixed by the Go team who regard sscanf as a mistake.

This only uses sscan for integers and uses the correct routine for
everything else.

This also implements parsing time.Duration

See: https://github.com/golang/go/issues/43306

fs/config/configstruct/internal_test.go

@@ -1,11 +1,9 @@
 package configstruct
 
 import (
-	"fmt"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func TestCamelToSnake(t *testing.T) {
@@ -22,39 +20,3 @@ func TestCamelToSnake(t *testing.T) {
 		assert.Equal(t, test.want, got, test.in)
 	}
 }
-
-func TestStringToInterface(t *testing.T) {
-	item := struct{ A int }{2}
-	for _, test := range []struct {
-		in   string
-		def  interface{}
-		want interface{}
-		err  string
-	}{
-		{"", string(""), "", ""},
-		{"   string   ", string(""), "   string   ", ""},
-		{"123", int(0), int(123), ""},
-		{"0x123", int(0), int(0x123), ""},
-		{"   0x123   ", int(0), int(0x123), ""},
-		{"-123", int(0), int(-123), ""},
-		{"0", false, false, ""},
-		{"1", false, true, ""},
-		{"FALSE", false, false, ""},
-		{"true", false, true, ""},
-		{"123", uint(0), uint(123), ""},
-		{"123", int64(0), int64(123), ""},
-		{"123x", int64(0), nil, "parsing \"123x\" as int64 failed: expected newline"},
-		{"truth", false, nil, "parsing \"truth\" as bool failed: syntax error scanning boolean"},
-		{"struct", item, nil, "parsing \"struct\" as struct { A int } failed: can't scan type: *struct { A int }"},
-	} {
-		what := fmt.Sprintf("parse %q as %T", test.in, test.def)
-		got, err := StringToInterface(test.def, test.in)
-		if test.err == "" {
-			require.NoError(t, err, what)
-			assert.Equal(t, test.want, got, what)
-		} else {
-			assert.Nil(t, got)
-			assert.EqualError(t, err, test.err, what)
-		}
-	}
-}