libprefetch: library to prefetch data using tracing.

1: This supports "mem" tracing only.
2: Replay option is modified to use "pread" instead
of readahead.

A simple utility binary "prefetch" is built which links to the library.

The binary allows record, replay and verifying the generated
metadata.

Bug: 362507272
Test: cargo test passes all unit tests.

Verify record, replay and dump options:

./prefetch record --duration 10 --path /data/test/trace-test
./prefetch replay --path /data/test/trace-test
./prefetch dump /data/test/trace-test --format csv

Change-Id: I1661e49183c6120d2878510e609571fe6d608bb5
Signed-off-by: Vikram Auradkar <auradkar@google.com>
Signed-off-by: Akilesh Kailash <akailash@google.com>