[v3] Binding runtime fixes

[fbbdev]

Description

As discussed with @leaanthony, this new PR splits off from #3347, which has been closed, all runtime side commits. These are independent of the binding generator and should already benefit users of the current version.

This new PR contains the following fixes (again, runtime only):

• Unmarshal bound method parameters to the correct type.
• Support for multiple error/non-error return values (previously at most 1 non-error and 1 error were supported).
• New test cases for BoundMethod.Call by @abichinger.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

The binding example and @abichinger's runtime tests run correctly.

• Windows
• macOS
• Linux

Test Configuration

Go Version     | go1.22.0                                                                      
Revision       | 12d12a33dec1d31f487b70f87bc31e80252f327c                                      
Modified       | true                                                                          
-buildmode     | exe                                                                           
-compiler      | gc                                                                            
CGO_CFLAGS     |                                                                               
CGO_CPPFLAGS   |                                                                               
CGO_CXXFLAGS   |                                                                               
CGO_ENABLED    | 1                                                                             
CGO_LDFLAGS    |                                                                               
DefaultGODEBUG | httplaxcontentlength=1,httpmuxgo121=1,tls10server=1,tlsrsakex=1,tlsunsafeekm=1
GOAMD64        | v1                                                                            
GOARCH         | amd64                                                                         
GOOS           | darwin                                                                        
vcs            | git                                                                           
vcs.modified   | true                                                                          
vcs.revision   | 12d12a33dec1d31f487b70f87bc31e80252f327c                                      
vcs.time       | 2024-02-21T12:40:32Z                                                          

# System
Name            | MacOS                                   
Version         | 12.6.6                                  
ID              | 21G646                                  
Branding        | Monterey                                
Platform        | darwin                                  
Architecture    | amd64                                   
Apple Silicon   | unknown                                 
CPU             | Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Xcode cli tools | 2395                                    
CPU             | Unknown                                 
GPU             | Unknown                                 
Memory          | Unknown                                 

# Diagnosis
 SUCCESS  Your system is ready for Wails development!

Checklist:

• I have updated website/src/pages/changelog.mdx with details of this PR
• My code follows the general coding style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[leaanthony]

Looks really good!