clients/stellarcore: Add support for Core's new `/getledgerentryraw` #4151

Job	Run time
Test (and push) verify-range image	2m 28s
Integration tests (ubuntu-20.04, 1.21, 12, 21)	1m 58s
Integration tests (ubuntu-20.04, 1.21, 16, 21)	2m 0s
Integration tests (ubuntu-20.04, 1.22, 12, 21)	1m 45s
Integration tests (ubuntu-20.04, 1.22, 16, 21)	1m 51s
Integration tests (ubuntu-22.04, 1.21, 12, 21)	2m 2s
Integration tests (ubuntu-22.04, 1.21, 16, 21)	1m 58s
Integration tests (ubuntu-22.04, 1.22, 12, 21)	2m 2s
Integration tests (ubuntu-22.04, 1.22, 16, 21)	2m 2s
	18m 6s

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