Add RPCErrorConvertible #83

Job	Run time
Benchmarks / Construct Benchmarks matrix	2s
Cxx interop / Construct Cxx interop matrix	7s
Soundness / Check generated code	1m 9s
Soundness / Swift license headers check	7s
Unit tests / Construct unit test matrix	3s
Examples / Windows (nightly-6.0)	3s
Examples / Windows (6.0)	2s
Examples / Windows (nightly-main)	2s
Examples / Linux (5.9)	23s
Examples / Linux (5.10)	23s
Examples / Linux (6.0)	5m 20s
Soundness / API breakage check	1m 9s
Soundness / Broken symlinks check	3s
Examples / Linux (nightly-6.0)	7m 4s
Examples / Linux (nightly-main)	2m 57s
Soundness / Documentation check	1m 17s
Soundness / License headers check	8s
Soundness / Format check	38s
Soundness / Python lint check	5s
Soundness / Shell check	30s
Soundness / Unacceptable language check	2s
Soundness / YAML lint check	3s
Benchmarks / Benchmarks / Linux (6.0)	2m 30s
Benchmarks / Benchmarks / Linux (nightly-6.0)	2m 53s
Benchmarks / Benchmarks / Linux (nightly-main)	3m 3s
Unit tests / Unit tests / Linux (6.0)	1m 20s
Unit tests / Unit tests / Linux (nightly-6.0)	1m 34s
Unit tests / Unit tests / Linux (nightly-main)	1m 35s
Cxx interop / Cxx interop / Linux (6.0)	53s
Cxx interop / Cxx interop / Linux (nightly-6.0)	1m 9s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 5s
	37m 39s

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