Fix '+' character in query parameters is not encoded when rewrite query parameter in mvc

[raccoonback]

Description

When a + character is included in an HTTP query parameter, it is currently interpreted as a space in cases where the BeforeFilterFunctions.rewriteRequestParameter() is applied. This may result in the parameter being misinterpreted on the server side compared to its original intent.

In this PR, we have applied precise encoding based on StandardCharsets.UTF_8 or replaced the use of UriUtils.encodeQueryParams() with a MvcUtils.encodeQueryParams() custom utility to ensure that the + character is correctly encoded as %2B.

Changes:

• Replacing + with %2B after standard encoding
• Added corresponding unit test

(The BeforeFilterFunctions.rewriteRequestParameter() method is only present in the main branch.)

For example.

[AS-IS]
"http://localhost/path?foo=A&bar=B%2B" -> "http://localhost/path?foo=A&bar=B " (The value of the 'bar' query parameter is encoded as a 'B '.)

[TO-BE]
"http://localhost/path?foo=A&bar=B%2B" -> "http://localhost/path?foo=A&bar=%2B"

[raccoonback]

@ryanjbaxter
Hello.
I've incorporated the same handling as in #3799 for the BeforeFilterFunctions.rewriteRequestParameter() filter, which currently exists only on the main branch.

Please take a look when you have a chance.
Thanks!

[ryanjbaxter]

Thanks for the ping. I actually made the change in BeforeFilterFunctions yesterday when merging #3799. The additional tests are useful though, thanks.