Documented handler max length of 128 characters isn't supported

Start with UserCodeLoader.cs, especially the parsing path around the reported line 242, and reproduce the dotnet6 case with the exact 128-character handler shown in the issue. Trace where the handler name loses its final character, then verify that the unchanged value invokes the handler successfully.

Describe the bug

AWS documentation says the Handler property has a max length 128 characters, but values exactly 128 characters long appear to be truncated to 127 characters in the dotnet6 Lambda runtime, and therefore fail.

Expected Behavior

A handler value exactly 128 characters long shouldn't be truncated and should invoke the handler method successfully.

Current Behavior

A handler value exactly 128 characters long, such as:

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX::XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.LambdaFunction::HandleAsync

produces a failure:

Amazon.Lambda.RuntimeSupport.ExceptionHandling.LambdaValidationException: Unable to find method 'HandleAsyn' in type 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.LambdaFunction' from assembly 'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX': Found no methods matching method name 'HandleAsyn'.
   at Amazon.Lambda.RuntimeSupport.Bootstrap.UserCodeLoader.FindCustomerMethod(Type type) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/UserCodeLoader.cs:line 242
   at Amazon.Lambda.RuntimeSupport.Bootstrap.UserCodeLoader.Init(Action`1 customerLoggingAction) in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/UserCodeLoader.cs:line 116
   at Amazon.Lambda.RuntimeSupport.Bootstrap.UserCodeInitializer.InitializeAsync() in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/UserCodeInitializer.cs:line 46
   at Amazon.Lambda.RuntimeSupport.LambdaBootstrap.InitializeAsync() in /src/Repo/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs:line 155

Reproduction Steps

1. Create a Lambda with a handler specification that is exactly 128 characters long.
2. Try to invoke the function.

Possible Solution

No response

Additional Information/Context

AWS Console shows the full value in the "Runtime settings" of the Lambda function, so it seems to be getting truncated somewhere in the Lambda runtime.

AWS .NET SDK and/or Package version used

N/A — this bug is independent from .NET SDK.

Targeted .NET Platform

.NET 6

Operating System and version

Amazon Linux 2