Remove redundant base64 encoding for private_key_base64 parameter.

[dmitry-workato]

The PKCS 8 file already provides base64 encoded string of the private key, no need for extra base64 encode/decode. This slows dows the connection with the database.

This PR removes extra base64 decode/encode step, improving the peformance of private key parsing for "private_key_base64" parameter. Notice, that the parameter is still "spark" serializable as it is a java String.

Unfortunately not backward compatible. If accepted by the maintainers I would be happy to create a new property: "private_key_pkcs8_pem" to make this change backward compatible.

Overview

SNOW-XXXXX

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[dmitry-workato]

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[sfc-gh-wfateem]

@dmitry-workato Just so it's clear, how would you use the parameter after this change? Are you providing only the base64 encoded content of the private key as a string, or are you also including the header
-----BEGIN ENCRYPTED PRIVATE KEY----- and the footer -----END ENCRYPTED PRIVATE KEY-----

[dmitry-workato]

@dmitry-workato Just so it's clear, how would you use the parameter after this change? Are you providing only the base64 encoded content of the private key as a string, or are you also including the header -----BEGIN ENCRYPTED PRIVATE KEY----- and the footer -----END ENCRYPTED PRIVATE KEY-----

Hey @sfc-gh-wfateem, the header/footer still would be part of the key. Would it work for all the cases?