fix: count XCTest suite totals once per run

[alexey1312]

Problem

XCTest prints the same Executed N tests line at each suite level: the nested suite, the .xctest bundle, and the Selected tests/All tests wrapper.

StreamingOutputParser added the wrapper count to the bundle count. += is correct for two .xctest bundles, because their tests are disjoint. The wrapper is not a sibling bundle — it contains the bundles, so the same tests were counted twice:

swift test --filter PluginFilesTests 2>&1 | xcsift -f toon
# passed_tests: 8   <- XCTest ran 4

A full run prints All tests, which failed the same condition and fell into the ignored fallback. This hid the defect outside of --filter.

The parser also added the duration of every summary line, so test_time counted each level again.

Fix

• Count the .xctest bundles only. The wrapper falls into the fallback slot, which the parser reads only when no bundle line exists — and there the wrapper is the last summary line, so the count stays correct.
• Read the run duration from the same suite level as the counts (resolvedXCTestDuration()).
• Rename testTimeAccumulator to swiftTestingTimeAccumulator, because it now holds the Swift Testing time only.
• Remove the selectedTestsSuite constant, which lost its last reference.

Result

Command	Before	After	Actual
swift test --filter … (2 tests)	passed_tests: 4, test_time: 0.006s	2, 0.003s	2, 0.003s
swift test (full)	435, ~45s	435, 15.157s	435, 15.157s

A filtered run with failures reported twice the failures. It now reports the true count.

Tests

Four regression cases in Tests/XCSiftCoreTests/ParsingTests.swift:

• passed count with the three repeated summary lines
• failure count with the same repetition
• test_time across suite levels
• durations of two separate .xctest bundles still add up (guards the disjoint case)

Full suite: 435 tests, 0 failures.

Fixes #83