Record how long a process takes to run

[Eric-Arellano]

This will allow us to answer questions like how much time caching (both local and remote) is saving vs. running the process again. For example, we can compare the cache time vs. the original recorded execution time.

To preserve the execution time, we must store the metadata both on FallibleProcessResultWithPlatform and ActionResult, which is what we serialize to for the local and remote caches. This introduces ProcessResultMetadata, which is a sibling to REAPI's ExecutedActionMetadata.

For remote execution, it's up to them to correctly set the ExecutedActionMetadata, which we then convert into ProcessResultMetadata. But for local execution, we can ensure we set up both types correctly.

The timings match what we see with the dynamic UI:

12:43:46.35 [INFO] Starting: Building pytest.pex with 5 requirements: ipdb, pygments, pytest-cov>=2.10.1,<2.12, pytest-icdiff, pytest>=6.0.1,<6.3
12:43:50.92 [INFO] Completed: Building pytest.pex with 5 requirements: ipdb, pygments, pytest-cov>=2.10.1,<2.12, pytest-icdiff, pytest>=6.0.1,<6.3
12:43:50.92 [INFO] Some(Duration { secs: 4, nanos: 565505208 })

[stuhood]

Looks good!

[Eric-Arellano]

The string is used for Err, but we then throw that away with .ok() so I left it empty.

[stuhood]

That's a weird API... ideally it would return a non-allocated error type with a Debug/Display impl, rather than passing in a string to format. But yea, this is fine for now.

We might consider logging at debug for negative times though...

[stuhood]

Thanks!