Enable escaping and unescaping of level parts

[CMCDragonkai]

Description

It is now possible to have arbitrary buffers as levels. So if the buffer has 0x00 or the separator byte, it is no longer a problem. We now automatically escape the separator bytes, and we also automatically escape any escaping byte too 0x5c.

Issues Fixed

• Relates https://github.com/MatrixAI/js-polykey/pull/366

Tasks

• [x] 1. Added escapeLevel
• [x] 2. Added unescapeLevel
• [x] 3. Updated parseKey to properly handle where 0x00 or 0x5c may appear within the level part
• [x] 4. Removed ErrorDBLevelSep and checkSepLevelPath and checkSepKeyPath.

Final checklist

• [x] Domain specific tests
• [x] Full tests
• [x] Updated inline-comment documentation
• [x] Lint fixed
• [x] Squash and rebased
• [x] Sanity check the final build