Fix the build
[websocket]: Fix ClientWebSocket.ReceiveAsync() with small buffer; bug #22704.

When calling ClientWebSocket.ReceiveAsync() with a buffer that's smaller than
the received chunk, we need to cache the header until next call.
Test XmlSerialization of element that requires implicit conversion.
Covers #20403.
ImplicitConvert was using method with wrong parameter and return type.
Changed method ImplicitConvert to internal static.
When needed serialized objects are now implicitly converted.
Fixes #20403.
Merge pull request #1270 from esdrubal/xmlimplicit

When needed serialized objects are now implicitly converted.
[mcs] Remove value type constrained type parameter instantiation optimization to handle parameterless struct constructors
[system.net.http] Encode ContentDisposition name. Fixes #18422
[System] Fixed Diagnostics.Switch ctor behavior for null parameters

Passing null to the displayName or description ctor parameter on MS.NET makes them equal to an empty string.
Fixed the Mono behavior to match .NET.
Merge pull request #1271 from akoeplinger/fix-switch-ctor

[System] Fixed Diagnostics.Switch ctor behavior for null parameters
[runtime] Redirect runtime logging to asl_log only on ios, not when running the cross compiler.
[runtime] Fix the RESOLTION_SCOPE->RESOLUTION_SCOPE typo.
[aot] Avoid a stack overflow if profiler enter-leave events are requested in the full-aot mode.
[system] Fixes failing test
[corlib] Enumerate all subdirectories including the first one. Fixes #22857
Add concurrent hashtable test to gitignore.