Fixes T5097. When linting a large list of paths (e.g., with --everything), do this internally:

$chunks = array_chunk($paths, 32);
foreach ($chunks as $chunk) {
  $this->lintChunk($chunk);
}

This keeps the advantages of parallelism and artifact sharing for future-based linters, without having memory usage grow in an unbounded way.

These callbacks changed:

• willLintPath(): Useless, no meaningful implementations. Internalized the required side effect and broke the hook.
• didRunLinters(): Now useless, with no meaningful implementations. Broke the hook.
• didLintPaths(): New hook which executes opposite willLintPaths().
• lintPath(): Linters no longer need to implement this method.

XHPAST now has an explicit way to release shared futures.

These minor changes also happened:

• Formalized the "linter ID", which is a semi-durable identifier for the cache.
• Removed linter -> exception explicit mapping, which was unused. We now just collect exceptions.
• We do the canRun() checks first (and separately) now.
• Share more service call profiling code.
• Fix an issue where the test harness would use the path on disk, even if configuration set a different path.

• Ran arc lint --everything in arcanist/.
  • With no chunking, saw unstable memory usage with a peak at 941 MB.
  • With chunk size 32, saw stable memory usage with a peak at 269 MB.
  • With chunk size 8, saw stable memory usage with a peak at 180 MB.
• Ran with --trace and saw profiling information.
• Created this diff.