C#: Fix CFG for assertions with multiple assertion arguments

[hvitved]

Follow-up on #4484.

The control-flow graph for M13 below

private void AssertTrueFalse(
       [System.Diagnostics.CodeAnalysis.DoesNotReturnIf(false)] bool condition1,
       [System.Diagnostics.CodeAnalysis.DoesNotReturnIf(true)] bool condition2,
       bool nonCondition)
{
}

void M13(bool b1, bool b2, bool b3)
{
    AssertTrueFalse(b1, b2, b3);
    return;
}

now becomes

(Note that the graph visualizer is, for some reason, not able to show both the true and false edges out of [assertion failure] access to parameter b2 (highlighted in red), possibly because the two edges have the same target.)

CSharp-Differences job here.

[tamasvajk]

LGTM

[hvitved]

CSharp-Changes looks good, so merging.