WIP: New mode to use transaction results to skip failed transaction and signature verification in catchup

[ThomasBrady]

Description

Resolves #X

Adds a new config option, CATCHUP_SKIP_KNOWN_RESULTS. When this config option is enabled, transaction results are downloaded from history archives for the catchup range. Failed transactions are not applied, and signatures are not verified.

Preliminary perf testing locally running catchup on 1000 ledgers:

user/system/total time seconds

*Baseline (no skipping):*     429 / 115 / 138s
*Skip Failed:*                373 / 99  / 114s  (1.14x / 1.16x / 1.21x speedup over baseline)
*Skip Failed + verification:* 334 / 88  / 95s   (1.28x / 1.30x / 1.45x speedup over baseline)

Remaining work:

• Run catchup in supercluster to get a more representative idea of the performance characteristics of the new mode
• Add more test coverage to test correct meta generation in this mode

Checklist

• Reviewed the contributing document
• Rebased on top of master (no merge commits)
• Ran clang-format v8.0.0 (via make format or the Visual Studio extension)
• Compiles
• Ran all tests
• If change impacts performance, include supporting evidence per the performance document