Add flexibility to the frequency_text in auto-generated issue titles

Issues that run quarterly but don't fall exactly on the start or end of a quarter would print "Yearly" in the title. This is because we're using a day_of_year array to provide flexibility on when during the quarter to generate the issue.

day_of_year defaults to a single value for a "Yearly" frequency of automated issues.

This MR creates the option to pass the frequency value to the script so that we can explicitly state, "Quarterly" or "Biannually" for example while using the flexibility of day_of_year.

Fixes https://gitlab.com/gitlab-com/Product/-/issues/3892#note_859113517