Adds json schema test cases for 11 added keywords

[spacether]

Adds (working) json schema test cases for 11 added 3.1.0 draft2020-12 json schema keywords

Keywords:

1. const: only string values are working because of these bugs in swagger parser:
   • 3.1.0 parsing of schemas containing const throws errors swagger-api/swagger-parser#1975
   • 3.1.0 spec processing const with boolean/integer value stored as string rather than boolean/Boolean/integer/Integer swagger-api/swagger-parser#1966
   • Note: one can accomplish the same constrain functionality by using enum with only one value in its list
2. contains
3. dependentRequired
   • 3.1.0 parsing of schema containing dependentRequired adds values not present in document swagger-api/swagger-parser#1978
4. dependentSchemas
5. maxContains
   • 3.1.0 parsing of document with max/minContains removes constraint if value is a float swagger-api/swagger-parser#1979
6. minContains
   • 3.1.0 parsing of document with max/minContains removes constraint if value is a float swagger-api/swagger-parser#1979
7. patternProperties
   • Note: this update fixes a bug where additionalProperties did not consider patternProperties
8. prefixItems
9. propertyNames
10. unevaluatedItems
11. unevaluatedProperties

When working on this PR, these bugs were found in swagger parser:

• 3.1.0 parsing of schemas containing const throws errors swagger-api/swagger-parser#1975
• 3.1.0 parsing of schema containing dependentRequired adds values not present in document swagger-api/swagger-parser#1978
• 3.1.0 parsing of document with max/minContains removes constraint if value is a float swagger-api/swagger-parser#1979

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