Add build statistics to Log Manifest Entry, exact build duration

[AvdLee]

I've updated LogManifestEntry for Xcode's latest format, adding statistics like number of warnings and errors. This allows to filter out failed builds without loading .xcactivitylog.

I've also changed the build duration from an Int into a Double and removed the rounding, so build durations are more precise. I believe it's up to the users of the framework to decide to round the build duration instead of us showing wrong build durations from the start.

[Iron-Ham]

cc: @AvdLee I'm likely to pull this into my fork which repairs the function/typecheck timings, since I think this would be quite useful for us

[AvdLee]

@aleksandergrzyb asked to re-review this. Small changes, just SwiftLint fixes and Sendable support!