feat(material): mat-slider thumbLabel support

[skrtheboss]

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
Adds support for enabling thumLabel in material slider.

What is the current behavior? (You can also link to an open issue here)

Step, max, min are supported on sliders through the templateOptions properties.
However, specifying whether the thumLabel is enabled or not is not supported.

What is the new behavior (if this is a feature change)?
You can enable the thumLabel via the templateOptions.

Please check if the PR fulfills these requirements

• The commit messages follow our guidelines: https://github.com/angular/angular.js/blob/master/CONTRIBUTING.md#commit-message-format
• A unit test has been written for this change.
• Running npm run build produced a successful build. (Unit testing can be done by running npm test;)
• My code has been linted. (npm run lint to do this. npm run build will fail if there are files not linted.)

Please provide a screenshot of this feature before and after your code changes, if applicable.

Other information:

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[aitboudad]

Thank you @skrtheboss!

[aitboudad]

added in 5.6.0 version.