solana: Add MacOS-compatible fuzz harness

[nvsriram]

This PR is based on #280. However, it uses the honggfuzz library, which does not work on Apple Silicon. Therefore, this PR attempts to make it work on macOS using alternative fuzzing libraries.

There are 3 main commits (corresponding to the 4 different approaches explored - check out this comment for more info) that can be checked out to debug the issues encountered:

1. Use libfuzzer-sys directly/ via cargo-fuzz
2. Use afl directly by copying over afl.rs
3. Use afl via afl crate

[nvsriram]

Summary of Approaches Explored:

• Two main fuzzers - Libfuzzer (via libfuzzer-sys) and AFL (via afl.rs) formed the basis of the approaches.
• Cargo tools to run these fuzzers - cargo-fuzz and cargo-afl were installed to build and run the fuzzers.

Approaches Explored:

Libfuzzer using libfuzzer-sys directly:

This involves following the Manual Usage section of the libfuzzer-sys README.
To test this, checkout 17d8c5d commit and run the following in the fuzz directory to build:

cargo rustc -- \
   -C passes='sancov-module' \
   -C llvm-args='-sanitizer-coverage-level=3' \
   -C llvm-args='-sanitizer-coverage-inline-8bit-counters' \
   -Z sanitizer=address

Libfuzzer using cargo-fuzz:

This involves following the cargo-fuzz README.
To test this, checkout 17d8c5d commit, install cargo-fuzz, and run the following in the fuzz directory:

cargo fuzz run <target>

AFL directly:

This involves copying over afl.rs src/lib.rs file and using it directly.
To test this, checkout d1689d5 commit, install cargo-afl, and run the following in the fuzz/src directory:

cargo afl build

AFL using afl crate:

This involves adding afl = "*" in Cargo.toml dependencies.
To test this, checkout f4219c1 commit, install cargo-afl, and run the following in the fuzz/src directory:

cargo afl build

Issues Encountered:

1. Cargo tools installation fails when attempted from within the repo as the rust-toolchain is set to use rustc 1.75.0-nightly while the tools' dependencies seem to require rustc 1.82 or newer. This can be solved by installing outside this repo via a newer rustc version.
2. Building/fuzzing targets fails with a similar error associated with older rustc version.
3. Example of the error thrown in the above cases is shown below:

   error: package `icu_normalizer_data v2.0.0` cannot be built because it requires rustc 1.82 or newer, while the currently active rustc version is 1.75.0-nightly
   Either upgrade to rustc 1.82 or newer, or use
   cargo update icu_normalizer_data@2.0.0 --precise ver
   where `ver` is the latest version of `icu_normalizer_data` supporting rustc 1.75.0-nightly
   

   This error repeats for various other packages like backtrace v0.3.75, icu_provider v2.0.0, icu_properties_data v2.0.1 etc. which makes manually installing precise versions to temporarily overcome the error also not possible.