feat(reexecution): add optional profiling support to benchmarking script

[Elvis339]

Why this should be merged

This patch is part of: ava-labs/firewood#1582

Adds profiling support to the C-Chain re-execution benchmark, enabling visibility into Rust FFI performance when using Firewood. When PROFILE=true, the binary is built with debug symbols and frame pointers, allowing profilers (pprof, perf, samply, Instruments) to resolve function names across the Go → CGO → Rust stack instead of showing opaque memory addresses.

How this works

When PROFILE=true is set:

1. Go build flags disable optimizations (-N) and inlining (-l) to preserve stack traces
2. DWARF debug info is kept uncompressed for profiler compatibility
3. CGO flags enable frame pointers and debug symbols for Rust FFI visibility
4. Binary is built to /tmp/vm_reexecute for post-run analysis

How this was tested

1. Baseline - build without profiling flags

# Build Go binary without profiling flags
go build -o /tmp/vm_reexecute \
  github.com/ava-labs/avalanchego/tests/reexecute/c

# Check for Rust debug info
dwarfdump --debug-info /tmp/vm_reexecute 2>/dev/null | grep -E "firewood::|storage::" | head -5

Output shows no Rust debug info

(no output)

2. Build WITH profiling flags:

# Sync Firewood at the required commit (includes profiling Nix package)
go run github.com/ava-labs/avalanchego/tests/fixture/polyrepo@6239973c9b \
  sync firewood@1dc00532d977c45d22cd5939cd5a692218c5ec94

# Build FFI with profiling (debug symbols + frame pointers)
cd firewood/ffi && rm -rf result && nix build .#profile
cd ../..

CGO_CFLAGS="-fno-omit-frame-pointer -g" \
go build -o /tmp/vm_reexecute \
  -gcflags="all=-N -l" \
  -ldflags="-compressdwarf=false" \
  github.com/ava-labs/avalanchego/tests/reexecute/c

# Check for Rust debug info
dwarfdump --debug-info /tmp/vm_reexecute 2>/dev/null | grep -E "firewood::|storage::" | head -10

Output shows resolved Rust type/function names:

DW_AT_type  (0x00af9e0b "core::result::Result<core::option::Option<firewood_storage::hashtype::trie_hash::TrieHash>, firewood::v2::api::Error>")
DW_AT_name  ("impl FnOnce() -> Result<firewood::db::Proposal<'db>, api::Error>")
DW_AT_type  (0x00af6bb2 "core::option::Option<firewood_storage::hashtype::trie_hash::TrieHash>")
DW_AT_type  (0x00b08ede "firewood::db::Proposal")
DW_AT_type  (0x00afa078 "core::result::Result<firewood_ffi::proposal::CreateProposalResult, firewood::v2::api::Error>")

This enables profilers to display human-readable Rust call stacks instead of raw memory addresses.

If empty output run:

cd firewood/ffi && nix-collect-garbage && \ 
    rm -rf /tmp/vm_reexecute && \
    nix build .#profile && \
    CGO_CFLAGS="-fno-omit-frame-pointer -g" \
    go build -o /tmp/vm_reexecute \
        -gcflags="all=-N -l" \
       -ldflags="-compressdwarf=false" \
       github.com/ava-labs/avalanchego/tests/reexecute/c

Need to be documented in RELEASES.md?

No

[Elvis339]

Requires merging #4790

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