Deprecate build optimizer getImportTslibTransformer

[alan-agius4]

🚀 Feature request

Description

We should deprecate build optimizer getImportTslibTransformer transformer and display a warning when ever a library needs this transformer. That way developers can file issue reports with the library authors.

Library authors should ship their code already optimized by enabling importHelpers in their tsconfig.

More info:
https://www.typescriptlang.org/docs/handbook/compiler-options.html https://github.com/Microsoft/tslib

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