ascanrules: Reflected XSS introduce param object

To facilitate further modifications and refactoring.

- CHANGELOG > Added maintenance note.
- CrossSiteScriptingScanRule > Introduce and leverage new param object.
- HtmlContextAnalyser > Throw an exception if the target param is empty
as that leads to an infinite loop.

Signed-off-by: kingthorin <[email protected]>

Author: kingthorin

addOns/ascanrules/CHANGELOG.md

@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - SQL Injection scan rule to start using ComparableResponse - part of the work to reduce False Positives.
 - Depends on an updated version of the Common Library add-on.
 - Due to it being 2025 and the mass adoption of HTTPS: De-prioritized plain HTTP payloads in the External Redirect scan rule.
+- Maintenance changes.
 
 ### Fixed
 - SQL Injection scan rule to treat a 500 response to an SQLi attack as a likely vulnerability.