Remove parser Context backtrace APIs and docs

[ehwan]

Summary

• Removed Backtrace from rusty_lr_core
• Removed deterministic Context::backtrace()
• Removed nondeterministic Context::backtraces()
• Removed README references to Context backtrace usage and --no-backtrace

[gemini-code-assist]

Code Review

This pull request introduces a major refactoring to optimize compiled binary size and simplify the parser API. The parser rules and DFA states are now serialized into flat static integer arrays and decoded lazily at runtime, replacing verbose static enum instantiations. Additionally, the %filter and %trace directives, along with backtracing functionality, have been removed. The Context structs now take the Parser as a generic parameter, eliminating the need to pass a parser reference to methods like feed, feed_location, and accept. Feedback on the changes suggests removing commented-out code placeholders in the Clone implementation of the nondeterministic Context.

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rusty_lr_core/src/parser/nondeterministic/context.rs (1817-1822)

Commented-out code should be removed to keep the codebase clean and maintainable. Since these fields are not meant to be cloned (as they are temporary fields populated during parsing), they can be safely omitted from the Clone implementation without leaving commented-out placeholders.

            _phantom: std::marker::PhantomData,
            ..Default::default()