validators: T7450: use PCRE2 instead of the outdated original PCRE

[dmbaturin]

Change summary

Value validation utilities currently use the pcre OCaml package. That package is based on the original PCRE library. Its latest release 8.45 is the last release and the original implementation is now declared EOL. That package is named libpcre3 in Debian, for some reason.

PCRE maintainers made a new release line called PCRE2 that has now replaced the original. Debian Trixie no longer includes the original implementation, only PCRE2. The package is called libpcre2. Yes, you read it right: libpcre2 is newer than libpcre3.

There are already OCaml bindings for PCRE2 — they are API-compatible, just use a different module name, so we only need to update those names and dependencies to make it work.

I also removed the build dependency from debian/control — that file doesn't list actual build dependencies like the OCaml toolchain anyway, so it's no use keeping libpcre there.

libpcre2 does exist in Debian Bookworm, so we can backport this change to 1.5/Circinus and possibly to 1.4/Sagitta.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe): dependency update.

Related Task(s)

Related PR(s)

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

[c-po]

Move to "newer" PCRE2 package even if the version number is smaller. Needed for ongoing effort updating to Debian Trixie.

Change looks reasonable.

[jestabro]

Update package as required for Trixie.