Update for v7 P3

Fix icsharpcode#2270: I love deleting code that causes problems and n…

…o longer makes any sense at all!

Fix async warning LoadDebugInfo

Fix icsharpcode#2185: Fix MemberIsHidden-check for local function dis…

…play structs: Async State Machines that looked like local function display structs were not hidden once local function decompilation was disabled. This led to code duplication in the generated pdb.

Avoid parentheses around lambdas where possible.

Adjust old `calli` test case to new function pointer syntax

Merge pull request icsharpcode#2135 from srutzky/patch-1

Fix "Offset" values in Optional Header metadata

Fix icsharpcode#2076: VS AddIn opens reference assembly.

Fix bugs ExportedTypeTableTreeNode

Fix icsharpcode#1772: Support EnumeratorCancellationAttribute

With this change, the async decompiler no longer gets confused by the logic disposing `this.<>x__combinedTokens`.