make dragonbox opt-in via -d:nimFpRoundtrips (#18504)

* make dragonbox opt-in via -d:nimFpRoundtrips

* make tests green again

* make tests green again

changelog.md

@@ -76,9 +76,6 @@
 - `json` and `jsonutils` now serialize NaN, Inf, -Inf as strings, so that
   `%[NaN, -Inf]` is the string `["nan","-inf"]` instead of `[nan,-inf]` which was invalid json.
 
-- `system.addFloat` now uses the "Dragonbox" algorithm, which ensures correct roundtrips of floating point
-  numbers, that the minimum length representation of a floating point number is used and correct rounding.
-  Use `-d:nimLegacyAddFloat` for a transition period.
 
 - `strformat` is now part of `include std/prelude`.
 
@@ -102,6 +99,12 @@
   added support for parenthesized expressions.
   added support for const string's instead of just string literals
 
+
+- `system.addFloat` and `system.$` now can produce string representations of floating point numbers
+  that are minimal in size and that "roundtrip" (via the "Dragonbox" algorithm). This currently has
+  to be enabled via `-d:nimFpRoundtrips`. It is expected that this behavior becomes the new default
+  in upcoming versions.
+
 - Fixed buffer overflow bugs in `net`
 
 - Exported `sslHandle` from `net` and `asyncnet`.
@@ -116,8 +119,6 @@
   the OpenSSL DLLs (e.g. libssl-1_1-x64.dll, libcrypto-1_1-x64.dll) you
   now also need to ship `cacert.pem` with your `.exe` file.
 
-- Make `{.requiresInit.}` pragma to work for `distinct` types.
-
 - `typetraits`:
   `distinctBase` now is identity instead of error for non distinct types.
   Added `enumLen` to return the number of elements in an enum.
@@ -468,7 +469,6 @@
   with `--styleCheck:error` or `--styleCheck:hint`.
 
 
-
 ## Tool changes
 
 - Latex doc generation is revised: output `.tex` files should be compiled