Measure config parse / file scan time, actual total time

[jakebailey]

In Strada, I can't tell if this time was omitted or just a part of the parse time (probably the latter). But we were totally omitting it in this repo, which hides the fact that config loading and file scanning takes a significant amount of time. Collect this number, and then ensure the total time actually includes everything.

See: #1062 (comment)

Config time:      0.120s
Parse time:       0.513s
Bind time:        0.100s
Check time:       5.719s
Emit time:        0.721s
Total time:       7.176s

This is going to make our total time stat longer, but it's more realistic, and we should totally go and optimize file scanning/matching to eliminate the use of regexp2.

As part of this, I've refactored System such that time fully goes through System, which I mistakenly did not do in my original PR moving this functionality into the execute pacakge.

[Copilot]

Pull Request Overview

This PR enhances the timing instrumentation by including the configuration file parse and file scan time in the overall compilation time measurement. Key changes include:

• Measuring and propagating config parse time in execute/tsc.go.
• Refactoring performCompilation to accept and assign the new configTime.
• Updating the system interfaces and test scaffolds (testsys_test.go and cmd/tsgo/sys.go) to support accurate total time measurement.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/execute/tsc.go	Added configTime measurement and adjusted totalTime computation
internal/execute/testsys_test.go	Added start time initialization and SinceStart() in the test system
internal/execute/system.go	Updated the System interface to include the SinceStart() method
internal/execute/outputs.go	Added reporting of config time if non-zero
cmd/tsgo/sys.go	Integrated a start time field and SinceStart() method for accurate timing

Comments suppressed due to low confidence (1)

internal/execute/tsc.go:197

• [nitpick] Consider adding a comment clarifying that sys.SinceStart() reports the elapsed time from system initialization, ensuring that maintainers understand the starting point of the total time measurement.

result.totalTime = sys.SinceStart()