Add severity option for validators

[hpmellema]

Background

Adds a property to set the severity of validators for the validate and build tasks.

The default severity for the build task remains WARNING while the default for the jarValidate task is updated to ERROR. This prevents the double-printing of warning events during the build so that by default the jarValidate task only prints validation events that would have caused it to fail.

Note: not all smithy-cli commands have a severity option.

Testing

Executed a build with and without this change and confirmed the

> Task :service:smithyFormat
Running smithy format

> Task :service:smithyBuild
Running smithy build

──  WARNING  ──────────────────────────────────────────────────────────── DocUrl
Shape: com.example.cafe.service#Order
File:  /Users/hpm/smithy-gradle-tutorial/service/model/service.smithy:25:1

24| @externalDocumentation(wikipedia: "https://en.wikipedia.org/wiki/Order")
25| resource Order {
  | ^

External url `https://en.wikipedia.org/wiki/Order` is invalid.


──  WARNING  ────────────────────────── HttpMethodSemantics.MissingReadonlyTrait
Shape: com.example.cafe.common#dummy
File:  /Users/hpm/smithy-gradle-tutorial/lib/build/libs/lib.jar!/META-INF/smithy/common.smithy:25:1

25| @http(code: 200, method: "GET", uri: "/yay")
  | ^
26| operation dummy {}

This operation uses the `GET` method in the `http` trait, but is not marked with
the readonly trait

SUCCESS: Validated 234 shapes (WARNING: 2)

Validated model, now starting projections...

──  source  ────────────────────────────────────────────────────────────────────
Completed projection source (234): /Users/hpm/smithy-gradle-tutorial/service/build/smithyprojections/service/source

Summary: Smithy built 1 projection(s), 3 plugin(s), and 4 artifacts

> Task :service:smithyJarValidate
Running smithy validate

──  WARNING  ────────────────────────── HttpMethodSemantics.MissingReadonlyTrait
Shape: com.example.cafe.common#dummy
File:  /Users/hpm/smithy-gradle-tutorial/lib/build/libs/lib.jar!/META-INF/smithy/common.smithy:25:1

25| @http(code: 200, method: "GET", uri: "/yay")
  | ^
26| operation dummy {}

This operation uses the `GET` method in the `http` trait, but is not marked with
the readonly trait


──  WARNING  ──────────────────────────────────────────────────────────── DocUrl
Shape: com.example.cafe.service#Order
File:  /Users/hpm/smithy-gradle-tutorial/service/build/libs/service.jar!/META-INF/smithy/service.smithy:25:1

24| @externalDocumentation(wikipedia: "https://en.wikipedia.org/wiki/Order")
25| resource Order {
  | ^

External url `https://en.wikipedia.org/wiki/Order` is invalid.

SUCCESS: Validated 234 shapes (WARNING: 2)


BUILD SUCCESSFUL in 4s
17 actionable tasks: 17 executed

After this change:

> Task :service:smithyFormat
Running smithy format

> Task :service:smithyBuild
Running smithy build

──  WARNING  ──────────────────────────────────────────────────────────── DocUrl
Shape: com.example.cafe.service#Order
File:  /Users/hpm/smithy-gradle-tutorial/service/model/service.smithy:25:1

24| @externalDocumentation(wikipedia: "https://en.wikipedia.org/wiki/Order")
25| resource Order {
  | ^

External url `https://en.wikipedia.org/wiki/Order` is invalid.


──  WARNING  ────────────────────────── HttpMethodSemantics.MissingReadonlyTrait
Shape: com.example.cafe.common#dummy
File:  /Users/hpm/smithy-gradle-tutorial/lib/build/libs/lib.jar!/META-INF/smithy/common.smithy:25:1

25| @http(code: 200, method: "GET", uri: "/yay")
  | ^
26| operation dummy {}

This operation uses the `GET` method in the `http` trait, but is not marked with
the readonly trait

SUCCESS: Validated 234 shapes (WARNING: 2)

Validated model, now starting projections...

──  source  ────────────────────────────────────────────────────────────────────
Completed projection source (234): /Users/hpm/smithy-gradle-tutorial/service/build/smithyprojections/service/source

Summary: Smithy built 1 projection(s), 3 plugin(s), and 4 artifacts

> Task :service:smithyJarValidate
Running smithy validate
SUCCESS: Validated 234 shapes (WARNING: 2)


BUILD SUCCESSFUL in 15s
17 actionable tasks: 17 executed

Links

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.