Improve uri.parseQuery to never raise an error (#16647)

In case of malformed query string where there is `=` on the value, handle
this character as part of the value instead of throwing an error.

The following query string should no longer crash a program:

    key=value&key2=x=1

It will be interpreted as [("key", "value"), ("key2", "x=1")]

This is correct according to latest WhatWG's HTML5 specification
recarding the urlencoded parser:
https://url.spec.whatwg.org/#concept-urlencoded-parser

Older behavior can be restored using the -d:nimLegacyParseQueryStrict
flag.

lib/pure/cgi.nim

@@ -84,11 +84,8 @@ proc getEncodedData(allowedMethods: set[RequestMethod]): string =
 iterator decodeData*(data: string): tuple[key, value: TaintedString] =
   ## Reads and decodes CGI data and yields the (name, value) pairs the
   ## data consists of.
-  try:
-    for (key, value) in uri.decodeQuery(data):
-      yield (key, value)
-  except UriParseError as e:
-    cgiError(e.msg)
+  for (key, value) in uri.decodeQuery(data):
+    yield (key, value)
 
 iterator decodeData*(allowedMethods: set[RequestMethod] =
        {methodNone, methodPost, methodGet}): tuple[key, value: TaintedString] =
@@ -96,11 +93,8 @@ iterator decodeData*(allowedMethods: set[RequestMethod] =
   ## data consists of. If the client does not use a method listed in the
   ## `allowedMethods` set, a `CgiError` exception is raised.
   let data = getEncodedData(allowedMethods)
-  try:
-    for (key, value) in uri.decodeQuery(data):
-      yield (key, value)
-  except UriParseError as e:
-    cgiError(e.msg)
+  for (key, value) in uri.decodeQuery(data):
+    yield (key, value)
 
 proc readData*(allowedMethods: set[RequestMethod] =
                {methodNone, methodPost, methodGet}): StringTableRef =