OpenAPI 3.1.0 support: example generation from JSON Schema 2020-12

[char0n]

The goal of this issue is to implement proper example generation for Try it out feature from JSON Schema 2020-12 schemas.

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The course of action here is to amend existing samples plugin to work with JSON Schema 2020-12 and not to blow up. We're aiming for quick win here. If time will allow us, we want to approach JSON Schema 2020-12 -> data generation in more complex way, similar to https://github.com/json-schema-faker/json-schema-faker

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TODO:

• extend ability to generate data for JSON Schema 2020-12 + OpenAPI 3.1 formats (#1, #2)
• add support for type keyword defined as an array
• add support for const keyword
• amend semantics for exclusiveMaximum and exclusiveMinimum keywords
• add support for multipleOf keyword
• add support for uniqueItems keyword
• add support for contains, minContains and maxContains keyword
• refactor support for maxLength, minLength and pattern keywords
• refactor support for maxProperties, minProperties and required keywords
• add support for contentEncoding keyword
• add support for contentMediaType keyword
• add support for contentSchema keyword
• separate constraints applicators for numbers and strings
• apply open/closed principle to plug custom encodings + media types
• priority order for handling default and example keyword
• add support for examples keyword
• add support for Boolean JSON Schema
• provide proper type keyword inference
• refactor merging schemas
• general cleanup

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What we'll not be adding support for (in alpha/beta phase):

NOTE: the list below needs to be itemized into individual GitHub issues

• dependentRequired keyword
• not keyword
• if keyword
• then keyword
• else keyword
• dependentSchemas
• prefixItems
• patternProperties
• propertyNames
• unevaluatedItems
• unevaluatedProperties

[char0n]

Functions from samples/fn.js are statically imported into different modules, which makes it impossible to override. We need to first refactor the code so that samples plugin is used as plugin and not as static ESM module.

PR where above mentioned problems were remedied: #8724

[char0n]

Missing keywords transformed into #8913