Create solana-sdk-wasm crate

[LucasSte]

Problem

solana-program and solana-sdk have both cdylib and rlib declared as crate types. Both crates are supposed to be used as libraries by other projects. This crate setting is specially problematic for SBF programs that import solana-program, since it does not permit us to run link-time optimizations:

   Compiling solana-program v2.2.1
error: lto can only be run for executables, cdylibs and static library outputs

error: could not compile `solana-program` (lib) due to 1 previous error

Summary of changes

1. Since the cdylib and the rlib types are only here to be compatible with the wasm target for wasm-pack, I created a new crate solana-sdk-wasm to hold all the items necessary for such a target.
2. Use only rlib for crate types in both solana-program and solana-sdk.
3. Updated the CI jobs accordingly.
4. Update the comments in program/src/lib.rs to correctly mention how to use the crate types.

Basic benchmark

This is not a comprehensive benchmark. I was just curious on the impact on a small Hello, Solana! program, like this:

entrypoint!(process_instruction);
fn process_instruction(
    _program_id: &Pubkey,
    accounts: &[AccountInfo],
    instruction_data: &[u8],
) -> ProgramResult {
    msg!("Hello, Solana!");
    Ok(())
}

These are the results:

No LTO: 18kb (18504 bytes) with 728 CUs consumed.
LTO enabled: 17kb (17576 bytes) with 638 CUs consumed.