Provide config to stellar-core as xdr instead of json #536

Job	Run time
amd64 / build-stellar-core	27s
amd64 / build-stellar-friendbot	44s
amd64 / build-stellar-soroban-rpc	48s
amd64 / build-stellar-horizon	2m 44s
arm64 / build-stellar-core	21s
arm64 / build-stellar-friendbot	2m 5s
arm64 / build-stellar-horizon	8m 12s
arm64 / build-stellar-soroban-rpc	2m 9s
amd64 / build	1m 22s
amd64 / test	0s
amd64 / push-pr	0s
amd64 / push-release	0s
arm64 / build	1m 30s
arm64 / test	0s
arm64 / push-pr	0s
arm64 / push-release	0s
manifest	0s
complete	1s
	20m 23s

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