memory allocation bugs

[g-r-a-n-t]

What was wrong?

Similar to #684.

I should look over all uses of avail and alloc.

To-Do

• OPTIONAL: Update Spec if applicable

• Add entry to the release notes (may forgo for trivial changes)

• Clean up commit history

[Y-Nak]

I've been considering this and now think that it'd be better to resolve this problem in #724.
When we switch to sonatina, this problem would arise again because it'll reuse allocated memory repeatedly.
We could resolve this by always zeroing memory when a variable is declared but this will cause performance degradation.

[Y-Nak]

But we should fix dynamic type encoding functions, where I wrongly assumed that allocated space for encoding is always zeroed. e.g., padding bytes should be explicitly zeroed here.

fe/crates/codegen/src/yul/runtime/abi.rs

Lines 139 to 147 in 7621ff9

	let func_def = function_definition! {
	function [func_name.ident()]([src.ident()], [dst.ident()]) -> [enc_size.ident()] {
	(let [string_len.ident()] := mload([src.expr()]))
	([enc_size.ident()] := add(32, (mul([string_len.expr()], 32))))
	(let data_size := add(32, [string_len.expr()]))
	([yul::Statement::Expression(provider.ptr_copy(db, src.expr(), dst.expr(), literal_expression!{data_size}, false, is_dst_storage))])
	([enc_size.ident()] := mul((div((add(data_size, 31)), 32)), 32))
	}
	};

[g-r-a-n-t]

see #747