Build failure on go 1.27

[scudette]

Since go 1.27 the default json implementation has changed - this breaks any projects who use this project as a dependency:

# go.lsp.dev/protocol
../../go/pkg/mod/go.lsp.dev/protocol@v1.0.2-0.20260831102204-fd045959937f/codec_helpers.go:183:13: assignment mismatch: 2 variables but tok.Int returns 1 value
../../go/pkg/mod/go.lsp.dev/protocol@v1.0.2-0.20260831102204-fd045959937f/codec_helpers.go:209:13: assignment mismatch: 2 variables but tok.Uint returns 1 value

To test the new implementation on older go versions use the env GOEXPERIMENT=jsonv2 which is the default on go 1.27

To temporarily revert go's implementation set the env GOEXPERIMENT=nojsonv2 or use the build tag goexperiment.nojsonv2