vtpm-quote: Add SHA256 PCR value extraction API

[surajssd]

This PR adds an API to extract all PCRs from SHA256 bank and store it in the quote. Alongwith this extraciton logic, it also adds a verification logic. Now users can call quote.verify_pcrs() to verify the PCR values.

How to test

Here is a sample code that can be used to verify the workings of code. Run the following steps from the root of the directory:

mkdir -p az-cvm-vtpm/az-snp-vtpm/example2/src

cat <<EOF > az-cvm-vtpm/az-snp-vtpm/example2/src/main.rs
use az_snp_vtpm::vtpm;
use bincode;
use std::error::Error;
use std::fs;

fn main() -> Result<(), Box<dyn Error>> {
    // Save the PCRs into binary file.
    let nonce = "challenge".as_bytes().to_vec();
    let quote = vtpm::get_quote(&nonce)?;
    let quote_encoded: Vec<u8> = bincode::serialize(&quote).unwrap();
    fs::write("/tmp/quote.bin", quote_encoded).expect("Unable to write file");

    // Verification logic
    let quote_bytes = fs::read("/tmp/quote.bin").expect("Unable to read file");
    let quote: vtpm::Quote = bincode::deserialize(&quote_bytes[..]).unwrap();
    println!("Verify PCRs: {:?}", quote.verify_pcrs()?);
    Ok(())
}
EOF

Here is Cargo.toml

cat <<EOF > az-cvm-vtpm/az-snp-vtpm/example2/Cargo.toml
[package]
name = "snp-example2"
version = "0.1.0"
edition = "2021"

[dependencies]
az-snp-vtpm.path = "../"
bincode.workspace = true
openssl.workspace = true
EOF

Make the following change:

diff --git az-cvm-vtpm/Cargo.toml az-cvm-vtpm/Cargo.toml
index 4a36f15..4eec2e9 100644
--- az-cvm-vtpm/Cargo.toml
+++ az-cvm-vtpm/Cargo.toml
@@ -13,6 +13,7 @@ members = [
        "az-snp-vtpm",
        "az-tdx-vtpm",
        "az-snp-vtpm/example",
+       "az-snp-vtpm/example2",
 ]

 [lib]

Finally run the code:

cd az-cvm-vtpm/az-snp-vtpm/example2
cargo build && sudo ../../target/debug/snp-example2

[mkulke]

let's bump a minor version of the tdx and snp crates in this PR

[surajssd]

I need to update other fixtures as well, because the test fails otherwise.

[surajssd]

I have updated the scriptures.