Fix wasm hotpatching for zero-sized data symbols

[tekacs]

Summary

• always record data symbols even when their size is zero in the parsed wasm linking table
• ensure GOT.mem fixups succeed during wasm hot-patching of WASM targets

Motivation

• the hot-patch pipeline resolves GOT.mem imports via the data_symbols map; when crates like tracing, tracing_subscriber, or sharded_slab emit zero-sized statics (e.g. sharded_slab::tid::REGISTRY, tracing_subscriber::layer::NONE_LAYER_MARKER, tracing_core::dispatcher::NO_SUBSCRIBER), wasm-ld writes them to the symbol table with size = 0
• the parser previously skipped those entries, so create_wasm_jump_table looked them up by index, failed with Failed to find data symbol by its index, and aborted hot-patching back to a full rebuild

Rationale

• keeping the zero-sized entries matches the wasm symbol table, and the subsequent logic only relies on the segment index and offset, so empty ranges are safe
• this avoids having to special-case call-sites later while unblocking WASM hot-patching in projects that depend on tracing

Testing

• dx new wasm-tracing (or reuse any Dioxus web app), add tracing = "0.1" and tracing-subscriber = "0.3", and initialize a subscriber in main
• run dx serve --hot-patch --web, edit src/main.rs to trigger a hot patch, and verify the build stays incremental without Failed to find data symbol by its index