Use vee-validate validation in the community programs components

Currently we are using frontend validation under ~/javascripts/subscription/components/community_program/ as a component-based that relies on the state of the components data. We need to convert that into project-style way with vee-validate (see example here).

As a part of this, we should also move away from duplicated states (example) and unnecessary watchers (example). Suggestion (not a hard requirement): perhaps the existing AcceptTerms component could be flexible enough to also handle TermsCheckbox and other "accept terms" situations?

More information in the original thread here: https://gitlab.com/gitlab-com/marketing/developer-relations/strategy-programs/open-source-program/gitlab-for-open-source/-/issues/51#note_2473519230