Remove duplicate PidExists/FindProcess, use pipe-fittings instead

[e-gineer]

Summary

• Delete pkg/utils/pid_exists.go which duplicated PidExists and FindProcess from pipe-fittings/v2/utils, removing the local copy that contains the same gopsutil int32 overflow bug causing failures on systems with UIDs > 2^31
• Update the sole caller in stop_services.go to use putils.PidExists (pipe-fittings version, which returns bool) instead of the local utils.PidExists (which returned (bool, error))
• This also resolves the TODO from Use pipe-fittings utils.PidExists func in service shutdown code instead of the steampipe version #4487 to consolidate onto the pipe-fittings version

Fixes #4951
Closes #4487

Note

The underlying gopsutil upgrade (to fix the int32 overflow in FindProcess) is tracked in turbot/pipe-fittings#781. That PR needs to land first for the full fix on systems with UIDs > 2^31. This PR removes the duplicate code so there's only one place to fix.

Test plan

• go mod tidy completes without errors
• go build ./... compiles successfully
• Verify service start/stop works correctly on a standard system
• Verify on a system with UID > 2^31 (after pipe-fittings#781 lands)

Testing

This PR is a pure code deletion + import consolidation — it removes the local duplicate pkg/utils/pid_exists.go and updates the one remaining caller to use the pipe-fittings version. Verified with go build ./... — no functional change, just removing duplication.

The actual int32 overflow fix is in the gopsutil upgrade tracked in turbot/pipe-fittings#781 / turbot/pipe-fittings#782. Once pipe-fittings releases with the gopsutil upgrade, steampipe should update its pipe-fittings dependency to pick up the fix.

🤖 Generated with Claude Code

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