Use the new reference assemblies package

* stop creating empty arrays over and over

* take a conservative starting size for sequence points collection

* don't use 0 as default size for generic arguments of a generic instance type.

* revert initial reserve of 4

* use existing Empty<T>.Array

* Remove whitespaces

Allocate GenericArguments collections with the right sizes

This makes it simpler to work with it when the instruction positions
are known in advance.

Add index based method to ILProcessor

The Interlocked.Exchange calls will ensure that the same object is
returned from each call even under a race.  That's not necessarily
required, but it should also make sure that no write re-ordering issues
occur on platforms that allow it.  And it also makes the possibility
of thread safety issues explicit.

Intialize it to null to match pattern for the other references.
Fixes the case were the lazy initialization would break when
public_key_token was Empty<byte>.Array.

Improves thread safety of lazy initializations

* add failing test for LocallyScopedConstantArray

* add LocallyScopedConstantArray target assembly

* ElementType.Array should be treated the same as object in ReadLocalConstant

* assert constant is null

* Style fixes

Co-authored-by: Jb Evain <jb@evain.net>

…648)

* Changing GetSymbolReader from PdbReaderProvider, when we create a Module from stream  we don't have the filename, and it's not necessary to create an EmbeddedPortablePdbReaderProvider, so I've moved the check to after the creation of EmbeddedPortablePdbReaderProvider.