Fixed pattern issue

[ckbaker10]

Checklist

• make test-all (UNIX) passes. CI will also test this
• unit and/or integration tests are included (if applicable)
• documentation is changed or added (if applicable)

Description of change

have-patterns matcher silently ignored the /i (case-insensitive) flag — and any other trailing flags — on /pattern/flags style patterns, causing those patterns to always fail when the output contained mixed-case text.

Root cause: sliceToPatterns classified a string as a regex only when it ended with a bare / (strings.HasSuffix(s, "/")). A pattern like /loglevel (verbose|info)/i ends with /i, so it fell through to the stringPattern branch and was evaluated with a strings.Contains check. The regex and the /i flag were both completely ignored. Additionally, newRegexPattern stripped only the literal trailing / character, so even patterns that did reach the regex path would have had any flags silently included in the compiled expression (causing a compile error or incorrect behaviour depending on the flag string).

Fix:

• Replaced the strings.HasSuffix(s, "/") check in sliceToPatterns with a new isRegexPattern helper that correctly recognises /pattern/, /pattern/i, /pattern/ms, etc. (allowing only valid Go RE2 inline flag characters i, m, s after the closing delimiter).
• Updated newRegexPattern to split at the last /, extract any trailing flags, and prepend them as a Go inline flag group ((?flags)) before compiling — e.g. /loglevel (verbose|info)/i is compiled as (?i)loglevel (verbose|info).
• All existing behaviour for plain /pattern/ patterns and literal string patterns is preserved.

Tests added (matchers/have_patterns_test.go):

• TestSliceToPatterns_FlaggedRegex — verifies that patterns with trailing flags are classified as regex patterns, not string-contains patterns.
• TestNewRegexPattern_CaseInsensitiveFlag — unit-tests newRegexPattern with the exact sshd -T output lines from the failing CIS audit controls (5.1.6, 5.1.12, 5.1.14, 5.1.15).
• TestHavePatternsMatcher_CaseInsensitiveFlag — end-to-end tests through the full HavePatternsMatcher, covering all four SSH-related CIS control failures where /i patterns failed against mixed-case output such as loglevel INFO.