Feature Request: Add Canadian postal code recognizer (CA_POSTAL_CODE)

[Joey239716]

Is your feature request related to a problem? Please describe.

Presidio's Canadian coverage is currently limited to a single recognizer
(CA_SIN). Canadian postal codes are common PII in address data, forms, and
free text, but there is no predefined recognizer for them, so they go
undetected using the built-in recognizer set.

Describe the solution you'd like

I would like to contribute a Canadian postal code recognizer to
presidio-analyzer, following the conventions of the existing postal-code
recognizers already in the project.

Suggested first scope:

• CA_POSTAL_CODE — a Canadian postal code
  in the standard A1A 1A1 format (Forward Sortation Area + Local Delivery Unit).
  • Similar postal-code recognizers already exist in Presidio, such as
    UK_POSTCODE and DE_PLZ, so this fits an established pattern.
  • UK_POSTCODE is the closest precedent: it is alphanumeric like Canada's and
    has no checksum, so detection relies on a tight regex plus context words.
  • Canada Post's format has clear public letter rules (the letters D, F, I, O,
    Q, U are never used, and W and Z are not used as the first letter), which
    keeps the regex specific and limits false positives.
  • Because the space between the FSA and LDU is often omitted in stored data, I
    plan to match both A1A 1A1 and A1A1A1, scoring the canonical spaced form
    higher — the same two-tier idea used by the existing CA_SIN recognizer for
    its delimited vs. undelimited forms.
  • Context words would be bilingual (English and French, e.g. "postal code" /
    "code postal"), since Canada is officially bilingual and CA_SIN already
    sets this precedent.

I also plan to update the relevant documentation as part of the contribution.

Describe alternatives you've considered

As of Presidio 2.2.363, the published recognizer set surfaces a few relevant
options:

• A single pattern with an optional space at one confidence level, as
  UK_POSTCODE does. This is simpler, but it cannot score the canonical spaced
  form higher than the space-omitted form.
• A user-defined custom PatternRecognizer. This works today, but a predefined
  recognizer benefits all Canadian users and keeps country coverage consistent.

Additional context

Format and letter-rule reference:
https://en.wikipedia.org/wiki/Postal_codes_in_Canada