Increase Safety when introspecting transactions

[bitzoic]

Description

When using thetx.sw library of the std-lib, if a bad input was given to the functions or a transaction did not exist, the functions would revert. Instead, they now return options so error may be caught.

Fixes

• WITNESS_LIMIT_POLICY and MATURITY_POLICY did not follow the fuel VM specs
• tx_maturity() did not follow the fuel VM specs
• tx_witness_pointer() now returns a pointer and is private
• tx_script_start_pointer() and tx_script_data_start_pointer() are now private

Breaking

There are a number of breaking changes in function return types.

• tx_maturity() now returns an Option<u32>.
  Before:

let my_tx_maturity: u64 = tx_maturity().unwrap()

After:

let my_tx_maturity: u32 = tx_maturity().unwrap()

• tx_script_length() now returns an Option<u64>
  Before:

let my_tx_script_length: u64 = tx_script_length();

After:

let my_tx_script_length: u64 = tx_script_length().unwrap();

• tx_script_data_length() now returns an Option<u64>
  Before:

let my_tx_script_data_length: u64 = tx_script_data_length();

After:

let my_tx_script_data_length: u64 = tx_script_data_length().unwrap();

• tx_witness_pointer() now returns an Option<raw_ptr> and is private
  Before:

let my_tx_witness_pointer: u64 = tx_witness_pointer(0);

After:

let my_tx_witness_pointer: raw_ptr = tx_witness_pointer(0).unwrap();

• tx_witness_data_length() now returns an Option<u64>
  Before:

let my_tx_witness_data_length: u64 = tx_witness_data_length(0);

After:

let my_tx_witness_data_length: u64 = tx_witness_data_length(0).unwrap();

• tx_witness_data() now returns an Option<T>
  Before:

let my_tx_witness_data: u64 = tx_witness_data::<u64>();

After:

let my_tx_witness_data: u64 = tx_witness_data::<u64>().unwrap();

• tx_script_start_pointer() now returns an Option<raw_ptr> and is private

let my_tx_script_start_pointer: raw_ptr = tx_script_start_pointer();

After:

let my_tx_script_start_pointer: raw_ptr = tx_script_start_pointer().unwrap();

• tx_script_data_start_pointer() now returns an Option<raw_ptr> and is private
  Before:

let my_tx_script_data_start_pointer: raw_ptr = tx_script_data_start_pointer();

After:

let my_tx_script_data_start_pointer: raw_ptr = tx_script_data_start_pointer().unwrap();

• tx_script_data() now returns an Option<T>
  Before:

let my_tx_script_data: u64 = tx_script_data::<u64>();

After:

let my_tx_script_data: u64 = tx_script_data::<u64>().unwrap();

• tx_script_bytecode() now returns an Option<T>
  Before:

let my_tx_script_bytecode: u64 = tx_script_bytecode::<u64>();

After:

let my_tx_script_bytecode: u64 = tx_script_bytecode::<u64>().unwrap();

• tx_script_bytecode_hash() now returns an Option<b256>
  Before:

let my_tx_script_bytecode_hash: b256 = tx_script_bytecode_hash();

After:

let my_tx_script_bytecode_hash: b256 = tx_script_bytecode_hash().unwrap()

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.