Reference type immutables

### What

Introduce ``code`` or ``contractdata`` as a new data location for data stored in the deployed bytecode as an extension of the current immutable mechanism.

### Why

Lifting the restrictions of the current immutable mechanism and transfer the merits to dynamic types.

### How

- [ ] https://github.com/ethereum/solidity/pull/13468

### Notes
- To be done in the design of Experimental Solidity.

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### Resources

1. #13323

Start by reviewing PR #13468 and the related issue #13323, then examine the current immutable mechanism and the Experimental Solidity design mentioned in the notes. Done means establishing and implementing the design for a code or contractdata location that extends immutables to dynamic types.

Written by the indexing model from the issue text.