[services] Tunnelbroker - CryptoTools tests.

Summary:
CryptoTools - is an internal toolset of functions for cryptography.

We perform tests on a rsaVerifyString() function, that checks the verification message signature signed by the public key provided.

Test Plan: Run yarn test-tunnelbroker-service all tests are run and succeed.

Reviewers: karol-bisztyga, palys-swm, varun

Reviewed By: karol-bisztyga, palys-swm

Subscribers: ashoat, palys-swm, Adrian, atul, karol-bisztyga, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3663