Incorrect PURL type for Alpine packages

### Description

Currently, we use `alpine` as the PURL type for Alpine packages, which is not in line with the latest [Package-URL Spec](https://github.com/package-url/purl-spec/blob/main/types-doc/apk-definition.md).
Alpine packages should use `apk` as the PURL type.

#### These package handler should use `apk` as default package type:

- https://github.com/aboutcode-org/scancode-toolkit/blob/6570c131e2821388286f661368a70e0120aaf2c6/src/packagedcode/alpine.py#L40
- https://github.com/aboutcode-org/scancode-toolkit/blob/6570c131e2821388286f661368a70e0120aaf2c6/src/packagedcode/alpine.py#L64
- https://github.com/aboutcode-org/scancode-toolkit/blob/6570c131e2821388286f661368a70e0120aaf2c6/src/packagedcode/alpine.py#L135

#### Related issues in other projects:

- https://github.com/aboutcode-org/univers/issues/191
- https://github.com/aboutcode-org/vulnerablecode/issues/2286