Some simplification to script number types

[someone235]

Unifying OpcodeData<i32/i64/Kip10I64> to use SizedEncodeInt for serialization.

Critical lines and explanation:

1. https://github.com/someone235/rusty-kaspa/blob/976313f0f4c492061689d84811b17ee1ea73cc8b/crypto/txscript/src/data_stack.rs#L178
   Here we limit any push_item<i32> to 4 bytes. This is fine since we nowhere use this method.
2. https://github.com/someone235/rusty-kaspa/blob/976313f0f4c492061689d84811b17ee1ea73cc8b/crypto/txscript/src/data_stack.rs#L166
   Here we limit any push_item<i64> to 8 bytes. Explanation for safety is in the code.
3. https://github.com/someone235/rusty-kaspa/blob/976313f0f4c492061689d84811b17ee1ea73cc8b/crypto/txscript/src/data_stack.rs#L173
   Here we limit any pop_items<i32> to 4 bytes, disallowing the use of i32::MIN. This is fine since in any place we use pop_items<i32> we also return an error if the number is negative.

[biryukovmaxim]

LGTM!

[michaelsutton]

3. https://github.com/someone235/rusty-kaspa/blob/976313f0f4c492061689d84811b17ee1ea73cc8b/crypto/txscript/src/data_stack.rs#L173
   Here we limit any pop_items<i32> to 4 bytes, disallowing the use of i32::MIN. This is fine since in any place we use pop_items<i32> we also return an error if the number is negative.

For the sake of accuracy, this was limited to 4 bytes also previously, through DEFAULT_SCRIPT_NUM_LEN.