Fix S5693 FP: custom fileUploadSizeLimit parameter ignored when parsing Web.config files

[cristian-ambrosini-sonarsource]

FP reported on SonarCommunity by Andrew Timson.

This rule has a configurable fileUploadSizeLimit parameter. The code for the rule appears to take the parameter into account when looking at attribute-based upload limits for both request size and request form size, but not when checking the configuration in Web.config; the latter sticks to the hardcoded 8 MB limit for both.

Using SonarQube Community Edition, Version 10.1 (build 73491)

<configuration>
    <system.web>
        <httpRuntime maxRequestLength="25600" />
        <!-- Compliant: maxRequestLength is exprimed in KB, so 25600KB = 25MB  -->
    </system.web>
    <system.webServer>
        <security>
            <requestFiltering>
                <requestLimits maxAllowedContentLength="26214400" />
                <!-- Compliant: maxAllowedContentLength is exprimed in bytes, so 26214400 = 25MB  -->
            </requestFiltering>
        </security>
    </system.webServer>
</configuration>

When fileUploadSizeLimit is set to 35000000, the above snippets are still flagged by the rule.