Suggest using ranges as protection against ReDos

What does this MR do and why?

Adds a suggestion in the Secure Coding Guidelines, under the Denial of Service (ReDoS) / Catastrophic Backtracking section, to specify reasonable ranges in regular expression patterns instead of the unbounded * and + which provides good resilience against ReDoS vulnerabilities, which is an issue we often see in our code.

/cc @gitlab-com/gl-security/appsec for feedback.

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