[mono] Fix swift lowering for InlineArray when static field occurs before instance field

[jkurdek]

Swift struct lowering algorithm on Mono fails when dealing with an InlineArray struct, which contains a static field before instance field. The result is a runtime crash.

Example of failing struct:

[InlineArray(16)]
struct Foo
{
  private static int someField = 1;
  internal byte payload;
}

Discovered in #108318

\cc @kotlarmilos

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