Stop using buffer-equal-constant-time

[idoshamun]

I noticed you use buffer-equal-constant-time indirectly through jws and gtoken.
buffer-equal-constant-time is a legacy and unsupported package since 2017. (Deprecation notice)
It causes some issues in combination with docker and some other environments.
I'd appreciate if you can consider switching it.
A solid alternative for jwt purposes is fast-jwt.

I have already switched jws here: https://github.com/idoshamun/google-auth-library-nodejs/tree/update-jwt-lib
But it's not enough as we also need to update gtoken

[sofisl]

Heads up that this library is not in active development, just in maintenance, so this might take a bit longer to get to. Thanks for submitting the issue!

[danielbankhead]

Thanks for reporting - we'll replace jws with another library.

Here's a tracking issue:

• refactor(deps): Migrate from jws library #1650