Gracefully handle deeply nested expressions, instead of blowing the stack

[yorickpeterse]

Please describe the bug

When parsing deeply nested expressions such as {{{{ repeat a lot of times }}}}, it's possible to consume all stack space and trigger a stack overflow. This is because our parser is implemented as a recursive descent parser, and specifically recurses to parse nested expressions.

To prevent this from happening, we should enforce a maximum nesting depth for expressions. This limit should be 64 such that it's unlikely to ever be hit in real code, but still protects against accidents.

This issue was first reported in #782. A (better) proposal on how to resolve this is found in #782 (comment).

Operating system

Fedora

Inko version

main