Trampolining and error recovery

[verytactical]

Try to write an implementation of seq, sel etc. where everything is a generator.

When error<Parser, "message"> is encountered, yield Recovered("message").

On entering a rule (a call), return child generator wrapped in Batch(), effectively trampolining it.

Make runParser(gen: () => Generator<...>) that

• when gen yields a Batch, push current generator on a const stack = []; and continue with the new generator
• when gen yields a Recovered, yield it

In order to prevent Tact running in browser from making the page freeze (before we implement better measures such as Worker; those require peculiar build process, major changes to API and making the code isomorphic)

• every N steps do a check
  • if delta on Date.now() between current and previous check is larger than M
    • await Promise.resolve(); to ensure other threads have time to do their job

Blocker to #1582