Move `package decimal` to be a subpackage of `package strconv`

core/decimal/decimal.odin → core/strconv/decimal/decimal.odin

@@ -1,6 +1,6 @@
 // Multiple precision decimal numbers
 // NOTE: This is only for floating point printing and nothing else
-package decimal
+package strconv_decimal
 
 Decimal :: struct {
 	digits:        [384]byte, // big-endian digits

core/strconv/generic_float.odin

@@ -1,6 +1,6 @@
 package strconv
 
-using import "core:decimal"
+using import "decimal"
 
 Int_Flag :: enum {
 	Prefix,