Support code coverage reporting for BPF programs

[riptl]

Problem

• Solana's BPF virtual machine does not support code coverage reports on smart contracts.
• Solana's fork of LLVM does not support DWARF debug information, which is required to map .text area content to line numbers via .debug_line.

Proposed Solution

• rbpf-cli can already trace program execution by recording all executed instructions.
• [SOL] re-enable debug info on SBF anza-xyz/llvm-project#25
• rbpf-cli should learn to translate trace information to code coverage (e.g. gcov) using DWARF debug info.