[libs] Refactor `System.Dynamic.Utils.DelegateHelpers` to utilize `UnsafeAccessorAttribute`

[ivanpovazan]

As discussed in: #90519 both:

• DynamicDelegateLightup
  

  runtime/src/libraries/System.Linq.Expressions/src/System/Dynamic/Utils/DelegateHelpers.cs

  Line 20 in b0d4502

  private static class DynamicDelegateLightup

• ForceAllowDynamicCodeLightup
  

  runtime/src/libraries/System.Linq.Expressions/src/System/Dynamic/Utils/DelegateHelpers.cs

  Line 31 in b0d4502

  private static class ForceAllowDynamicCodeLightup

should utilize UnsafeAccessorAttribute to simplify the logic of accessing the internal static methods in Delegate and AssemblyBuilder respectfully.

This would additionally remove the need for Internal.Runtime.Augments.DynamicDelegateAugments forwarder and simplify the code in general.

For reference: similar refactoring has been done in: #89706

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Issue Details

---

As discussed in: #90519 both:

• DynamicDelegateLightup
  

  runtime/src/libraries/System.Linq.Expressions/src/System/Dynamic/Utils/DelegateHelpers.cs

  Line 20 in b0d4502

  private static class DynamicDelegateLightup

• ForceAllowDynamicCodeLightup
  

  runtime/src/libraries/System.Linq.Expressions/src/System/Dynamic/Utils/DelegateHelpers.cs

  Line 31 in b0d4502

  private static class ForceAllowDynamicCodeLightup

should utilize UnsafeAccessorAttribute to simplify the logic of accessing the internal static methods in Delegate and AssemblyBuilder respectfully.

This would additionally remove the need for Internal.Runtime.Augments.DynamicDelegateAugments forwarder and simplify the code in general.

For reference: similar refactoring has been done in: #89706

Author:	ivanpovazan
Assignees:	ivanpovazan
Labels:	area-System.Linq.Expressions
Milestone:	9.0.0

[SamMonoRT]

cc @fanyang-mono fyi

[jkotas]

Fixed by #115583