fix(cognito): use npm package over core module

[meMuszr]

Description of changes

Avoid core modules for browser builds

Issue #, if available

Description of how you validated changes

Checklist

• [ x] PR description included
• [ x] yarn test passes

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

[meMuszr]

@jimblanc something you can have a look at please?

[nadetastic]

Hi @meMuszr thank you for your contribution. Looking at the changes that you are making, they may re-introduce a recent issue that was resolved by this PR - where it essential does the opposite of what your PR is doing. Due to this, I’ll go ahead and close this PR out. Thanks!

[meMuszr]

@nadetastic thanks for your comment. Bummer it got closed prematurely, open to a discussion or no? Looks like the buffer dependency in both that package the linked PR is addressing as well as this one is sitting two major versions behind (and more importantly in the cognito-identity-js package not getting used). Have other solutions been ruled out? Otherwise I'll go ahead and file an issue against the fact that the node module buffer is being used incorrectly in a web context.