Add Bolt as a Payment Method Option (Solidus 2.11)

[piyushswain]

This PR adds bolt as a payment method option during solidus installation.
The install_generator.rb file has been updated to add Bolt as an optional payment method during solidus installation.

The Bolt option in the payment method installs the solidus_bolt gem.

Ref solidusio/solidus_bolt#109

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[waiting-for-dev]

Closing, as we're only going to add it in the latest version (it doesn't make sense to start a new project with an old version).