C# 14 support

[damieng]

Now that C# version 14 is settling down we need to look at what changes are needed to support new syntax.

• Extension members
• Null-conditional assignment
• nameof supports unbound generic types
• More implicit conversions for Span and ReadOnlySpan
• Modifiers on simple lambda parameters
• field backed properties
• partial events and constructors
• user-defined compound assignment operators