Fix FP S2589: Assignment for captures are ignored

[martin-strecker-sonarsource]

Originally reported at https://community.sonarsource.com/t/false-positive-for-s2589/114185

Description

Any mutation of a captured variable is ignored. This applies to captures by delegates and by local functions. See also #8885

Repro steps

public bool ForEachTest(List<string> licenseData)
{
    var found = false;
    licenseData.ForEach(license => found = true); // Assignment in "ForEach"
    if (!found) // Noncompliant FP
    {
        Console.WriteLine("No License for artifact type");
    }
    return found;
}

public bool SelectTest(List<string> licenseData)
{
    var found = false;
    licenseData.Select(license => found = true).Any(); // Assignment in "Select"
    if (!found) // Noncompliant FP
    {
        Console.WriteLine("No License for artifact type");
    }
    return found;
}

public bool ActionTest()
{
    var found = false;
    Action assign = () => found = true; // Assignment in some delegate
    assign();
    if (!found) // Noncompliant FP
    {
        Console.WriteLine("No License for artifact type");
    }
    return found;
}

public bool LocalFunctionTest()
{
    var found = false;
    Assign();
    if (!found) // Noncompliant FP
    {
        Console.WriteLine("No License for artifact type");
    }
    return found;

    void Assign() => found = true; // Assignment in local function
}

Expected behavior

Do not raise on mutated captured variables or learn inside the delegate/local function body.

Actual behavior

FP for S2589

Known workarounds

Do not mutate capture variables.