Support the phone number filter `region` property for locale-aware detection

[jzonthemtn]

Summary

Support a new optional region property on the phone number filter (filterPhoneNumber.region) so a policy can set the default region(s) used to detect phone numbers written without an international + country code. This is the runtime half of PhiSQL RFC philterd/phisql#22.

region is a single ISO 3166-1 alpha-2 string or an array of them (default "US"). Numbers with a + prefix are detected regardless; the region only affects bare national-format numbers.

Requires phisql 1.2.0, the schema version that defines filterPhoneNumber.region. Blocked until this schema version is targeted.

Prerequisite

phileas-python's phone filter (phileas/filters/phone_number_filter.py) is currently a set of NANP regex patterns and does not use a phone-number library. The phonenumbers package (the Python port of libphonenumber) is not a dependency. region has no meaning until detection runs through phonenumbers, so this depends on first adopting phonenumbers and using its PhoneNumberMatcher / find API (the analog of the Java libphonenumber path). That library adoption is the prerequisite and should land first (and would also close the international-detection gap that the regex filter has today).

What to change (after adopting phonenumbers)

1. Add phonenumbers as a dependency and detect phone numbers with it (default region "US", a leniency comparable to libphonenumber POSSIBLE).
2. Read region from the phone filter config, accepting either a string or a list of strings (default ["US"]).
3. Scan once per configured region and merge, de-duplicating overlapping spans. +-prefixed numbers are found regardless of region.

Backward compatibility

Additive. A policy without region behaves as the default "US".

Acceptance criteria

• phonenumbers-based detection is in place (prerequisite).
• The phone filter reads region as either a string or a list, defaulting to US.
• A policy with region: "GB" detects UK national-format numbers; region: ["US","GB","FR"] detects national-format numbers from each.
• +-prefixed international numbers are detected regardless of region.
• Multi-region results are de-duplicated.
• Behavior matches the Java and .NET Phileas implementations for the same policy and inputs.
• The package targets phisql 1.2.0.

Reference: PhiSQL RFC philterd/phisql#22.

[jzonthemtn]

Prerequisite filed: #49 (adopt the phonenumbers library, closing the international-detection gap). The region support in this issue builds on that; #49 should land first.