Move transforms that read IL to an earlier stage in the decompiler pipeline

[siegfriedpammer]

The following transforms introduce large sub-trees into the ILAst of an ILFunction, but happen relatively late in the decompiler pipeline:

• DelegateConstruction
• LocalFunctionDecompiler

[dgrunwald]

Primary reason is that we want to also move the DisplayClass-transform to an earlier point; because it turns field accesses into local variable accesses; and some transforms (e.g. using) require local variables.

[dgrunwald]

Problem: display classes are also used for expression trees, so moving lambdas/local functions to an earlier point is not sufficient to fix all problems with the using transform.

And there's very little reason to move lambdas/local functions when we can't also move the display class transform.