zimg: modernize

[madebr]

Specify library name and version: zimg/all

For conan-io/hooks#320

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• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[conan-center-bot]

All green in build 1 (deee13f942aae3f86bc40638cf148cab7731ac3b):

• zimg/3.0.2@:
  All packages built successfully! (All logs)

• zimg/3.0.1@:
  All packages built successfully! (All logs)

• zimg/2.9.3@:
  All packages built successfully! (All logs)