Generalize the pipefail false-negatives fix from #12919

[saintstack]

Move output_contains from s3client_test.sh to tests_common.sh and add output_matches, output_matches_i, output_matches_E variants for regex and case-insensitive matching. All use here-strings (<<<) instead of echo|grep pipes, avoiding false negatives from SIGPIPE when pipefail is enabled.

Convert 26 of 28 echo|grep -q instances across test scripts. Two chained grep patterns (grep -i | grep -qvi) are left unchanged.

Also make backup_tests_common.sh source tests_common.sh so the helpers are available in backup test utilities.

[foundationdb-ci]

Result of foundationdb-pr-clang-ide on Linux RHEL 9

• Commit ID: 256b94a
• Duration 0:22:39
• Result: ✅ SUCCEEDED
• Error: N/A
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[foundationdb-ci]

Result of foundationdb-pr-macos-m1 on macOS Ventura 13.x

• Commit ID: 256b94a
• Duration 0:34:01
• Result: ✅ SUCCEEDED
• Error: N/A
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[foundationdb-ci]

Result of foundationdb-pr-clang-arm on Linux CentOS 7

• Commit ID: 256b94a
• Duration 0:42:55
• Result: ✅ SUCCEEDED
• Error: N/A
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[foundationdb-ci]

Result of foundationdb-pr-macos on macOS Ventura 13.x

• Commit ID: 256b94a
• Duration 0:46:31
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[foundationdb-ci]

Result of foundationdb-pr on Linux RHEL 9

• Commit ID: 256b94a
• Duration 1:00:02
• Result: ✅ SUCCEEDED
• Error: N/A
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[foundationdb-ci]

Result of foundationdb-pr-clang on Linux RHEL 9

• Commit ID: 256b94a
• Duration 1:00:44
• Result: ✅ SUCCEEDED
• Error: N/A
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[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux RHEL 9

• Commit ID: 256b94a
• Duration 2:09:07
• Result: ✅ SUCCEEDED
• Error: N/A
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