fix: [SQLite3] getFieldData() returns incorrect primary_key values

[kenjis]

Description
The return type is integer, not boolean.

primary_key - integer 1 if the column is a primary key (all integer 1, even if there are multiple primary keys), otherwise integer 0 (This field is currently only available for MySQL and SQLite3)
See https://codeigniter4.github.io/CodeIgniter4/database/metadata.html#retrieve-field-metadata

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide