extract-base64 command

[YamatoSecurity]

Similar to https://github.com/fukusuket/base64-utf-detect and Yamato-Security/hayabusa#1512 but will have the advantage of being able to extract base64 strings from the scriptblock logs that are not fragmented.

@fukusuket This is low priority so we can do this one after we release Hayabusa 3.0.