[Ledger] Enhance Ledger Class

[lllwvlvwlll]

This enhancement reimplements the feature for fetching additional keys from a ledger device, which was disabled as part of #2219 .
Currently, the authentication interface for ledger is extremely functional, hammering the connection open/close on every request. This introduces an issue when trying to resolve multiple events at once (like checking ledger status and requesting additional keys).

The proposed implementation path for this feature is a minor rearchitecture of the ledger classes and their relationship with the
LoginLedgerNanoS component to allow a persistent connection which handles interfacing needs. This should also significantly improve application performance when on the component is active since it reduces the overhead of negotiating the interface for every request.

The proposed enhancement would not impact the signing features of the application.

[ixje]

Is the connection negotiation really that slow? I always had the feeling it was the actual public key grabbing on the device. I will actually test it.

fyi; I like the idea of redesigning the ledger classes. I kind of went with the "fastest way" a.k.a copy the NEO2 stuff and adjust since the component and actions felt so tightly coupled.

[lllwvlvwlll]

The performance enhancement is a secondary benefit to the preventing of overlapping serial connections.

The bus isn't locked(I suspect) so a "close" from a parallel request is killing the connection before the public keys return. This also occurs inversely where the public key requests are getting getDeviceInfo and getAppName which is being communicated on the interface.

I do think there is a significant overhead from negotiating a connection and closing before each message, but its purely based on experience in other system. I don't know how substantial it will be.

[ixje]

I did some testing with the Python lib but should be reflective for JS

• Acquiring USB conn - 00:079 seconds
• Acquiring 1 public key - 01:238 seconds

[lllwvlvwlll]

Renaming this issue to be an enhancement which can be handled after N3 Ledger integration since the Fetch Multiple Keys defect was mitigated using a different approach.