Move xdr2json to a more non-rpc user friendly location

[chowbao]

xdr2json is currently embedded within stellar-rpc/internal. But this xdr2json might be the only existing golang xdr2json representation. It would be nice to either

• Move xdr2json to a higher level directory (closer to main/)
• Or separate out into it's own library/repo
• Or some other option that is not leaving it embedded in the stellar-rpc application

https://github.com/chowbao/go-stellar-xdr-json
Example separate library/repo where all the rust is precompiled so other golang projects can import xdr2json without the cgo targets. They only need to import "github.com/chowbao/go-stellar-xdr-json/xdr2json"

The precompiled rust looks good for a first pass
TODO:

• Create a new stellar/go-stellar-xdr-json repo (public)
• Add github actions/workflow to automatically compile and commit the rust object files
• If possible also automate the pulling of new releases from the stellar/rs-stellar-xdr

[chowbao]

They're is favor in moving this to it's own repo from this slack thread

[chowbao]

New repo and initial code committed https://github.com/stellar/go-stellar-xdr-json