Add tests for Multiple Matches

[UdeshyaDhungana]

• Add tests for Grep/Multiple Matches Extension

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Note

Adds Multiple Matches (-o) test suite and integrates new stages (cj0, ss2, bo4) into tester, course config, and Makefile.

• Tests (Multiple Matches):
  • Add testMultipleMatchesSingleMatch, testMultipleMatchesSingleLine, testMultipleMatchesMultipleLines in internal/ to validate -o -E output across single/multi-line inputs.
• Test harness:
  • Introduce PrintMatchesOnlyTestCase and PrintMatchesOnlyTestCaseCollection in internal/test_cases/print_matches_only_test_case.go to emulate grep -o -E, assert exit codes, and verify ordered match outputs.
• Tester wiring:
  • Register stages cj0, ss2, bo4 in internal/tester_definition.go (with timeout for cj0).
• Course config:
  • Add new extension multiple-matches with stages cj0, ss2, bo4 to internal/test_helpers/course_definition.yml and descriptions.
• Makefile:
  • Add test_multiple_matches_with_grep target and include it in test_all.

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[rohitpaulk]

A whole 60 seconds? That's kinda wild - is there a reason we need to change this from the default @UdeshyaDhungana?

[rohitpaulk]

Can be done in the challenge PR but noting here: let's order extensions like this:

• Printing matches
• Multiple matches
• Highlighting
• File search
• Quantifiers
• Backreferences