Improves stellar-core-debug-info script and adds docs (#4553) #6361

Job	Run time
rust-check-git-rev-deps	19s
build (gcc, current)	1h 14m 15s
fmt	15s
build (gcc, current, --check-test-tx-meta)	55m 36s
cargo-deny (advisories)	52s
build (gcc, next)	31m 23s
cargo-deny (bans licenses sources)	48s
build (gcc, next, --check-test-tx-meta)	16m 32s
build (clang, current)	26m 49s
build (clang, current, --check-test-tx-meta)	15m 10s
build (clang, next)	28m 16s
build (clang, next, --check-test-tx-meta)	15m 47s
complete	1s
	4h 26m 3s

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