Walletwasabi: Make QR code Capital letter Bech32

[MaxHillebrand]

Problem

Currently the QR code is in lower case letters, this is inefficient.

Solution

According to this research by @bitcoinops, bech32 was designed so that the QR code is very efficient, if the address is encoded in capital letters.

[jmacato]

This is currently blocked by QrCodeNet not detecting proper encoding modes.. I tried encoding uppercase addresses on our QrCodeNet and it doesnt properly detect the correct encoding, hence not shrinking the QR code.

[lontivero]

It doesn't detect it because I think we removed that part.

[jmacato]

@lontivero i see.. was it too buggy with the character encoding detection? because other QR encoders online does shrink the matrix

[lontivero]

@jmacato take a look at this commit: 1e7278469 where I removed all the encodings to simplify the QrCodeNet code. The only encoding used by wasabi is the EightBitByteEncoder but I think it could be good to change it by the removed AlphanumericEncoder. Anyway, that encoder does not make any difference regarding lower-case characters and upper-case characters neither.

[jmacato]

@lontivero I agree, though we should also consider to replace QrCodeNet with a newer library (https://github.com/codebude/QRCoder). I can strip that one down and use it for this. This feature is also useful because the larger the qr code blocks are, the better they'd be detected at farther distance.

[jmacato]

@lontivero I can confirm that QRCoder generates the proper and smaller QR code for uppercase alphanumerics.