Rework the hbs to lit compiler

[vladitasev]

A lot of technical debt has accumulated in the hbs compiler.

TODO:

• merge the hbs2lit and hbs2ui5 libs (currently there is not enough logical separation to justify the existence of both)
• delete unneeded files, rename files that end with 2
• overall restructure the code and improve readability
• document better
• enforce eslint and improve code quality
• write tests

Eventually, even make this a standalone package in our repo with its own lifecycle and test system. Don't burden the tools package with this extra complexity and dependencies.

[vladitasev]

Fix the bug with ../ giving the root context instead of the one-level-up context. Implement @root for getting the root context