AVM improvements

[sirasistant]

This ticket tracks a list of possible improvements for the public VM and the reasoning behind every item (ordered by need!):

Wishlist

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1. **Adding a u1 tag along with the current u8, u16, u32, u64 and field**. Booleans are widely used, and without u1 memory cells the compiler will need to codegen bit masking on top of u8s to handle casts to u1 and some u1 arithmetic operations. We could also swap u16 with u1 since booleans will probably see much more use than u16s. #7054
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2. Adding integer division for fields. This one is needed to be able to perform to_radix. to_radix is used to decompose a field in an array of items that go from 0 to radix. This is implemented via a loop of integer divisions.
3. LT/LTE opcode support for field type. Brillig range checks are implemented as field comparisons thus requiring LT/LTE over fields.
4. Allow the set opcode to have inTag of field. It's very typical that we create field constants where the actual value is less than 128 bits, to operate with it as a field. This would save some cast opcodes that aren't really necessary.
5. Adding a relative direct addressing mode. If we have relative addressing, we can efficiently implement having a proper stack instead of the current solution of just having one stack frame that we dump/restore to heap on every internal call.
6. Adding a relative indirect addressing mode. If we have both relative direct and relative indirect we can operate efficiently with all the items in the stack, being them pointers or immediate values.

Most of these items have workarounds but implementing them would enable the compiler to generate smaller bytecodes for the same programs.