Add metadata filtering to the Images binding hosted.list()

[Monark-Arkmon]

Adds an optional metadataFilters option to env.IMAGES.hosted.list() so
Workers can filter hosted-image lists by custom metadata, matching the Images
REST API. Operators: eq (also the implicit form), in, gt, gte, lt,
lte; dot-notation for nested fields; multiple fields combined with AND. Shape
follows the Vectorize metadata-filtering API.

hosted.list() forwards options to the hosted-images service over RPC
unchanged, so this is the type definition plus test coverage; the upstream
service does the filtering. images-api-test exercises each operator through
the mocked upstream.

Draft: companion to workers-sdk #14510; API shape still being finalised.

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[Monark-Arkmon]

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