fix(dotnet): parse MTP multi-line test run summary

[guyoron1]

Summary

The Microsoft Testing Platform (.NET 10) writes test results in a multi-line
format that the existing regexes couldn't match, causing rtk dotnet test to
report "counts unavailable" even when tests passed successfully.

Before: ok dotnet test: completed (binlog-only mode, counts unavailable, 0 warnings)
After: ok dotnet test: 72 tests passed, 0 warnings in 1 projects (1s 672ms)

Root cause

MTP outputs a multi-line summary:

Test run summary: Passed!
  total: 72
  failed: 0
  succeeded: 72
  skipped: 0
  duration: 1s 672ms

But TEST_RESULT_RE expects VSTest's single-line Passed! - Failed: 0, Passed: 72, ...
format, and TEST_SUMMARY_RE expects single-line Test summary: total: 72, failed: 0, ....
Neither matches the multi-line MTP format, so all counts stay at zero.

Fix

Add MTP_MULTILINE_SUMMARY_RE as a fallback regex in parse_test_from_text. It only
triggers when the earlier regexes find no counts (summary.total == 0), keeping backward
compatibility with VSTest and single-line MTP formats.

Changes

• src/cmds/dotnet/binlog.rs: Add MTP_MULTILINE_SUMMARY_RE lazy_static regex and
  fallback parsing block in parse_test_from_text
• Two new unit tests: test_parse_test_from_text_mtp_multiline_passed and
  test_parse_test_from_text_mtp_multiline_failed

Test plan

• cargo fmt --all — no formatting issues
• cargo clippy --all-targets — no warnings
• cargo test --all — all tests pass (including 2 new MTP tests)
• New tests verify both Passed! and Failed! MTP summary formats

Fixes #2279