Support amaranth~=0.5

[antoinevg]

Currently cynthion gateware targets "amaranth~=0.4.0". The next Amaranth release will be 0.5 which will bring some substantial changes: https://github.com/amaranth-lang/amaranth/blob/main/docs/changes.rst#version-05-unreleased

Some of these affect the cynthion, luna and luna-soc gateware directly and, at the time of writing, include:

• Final deprecation of the Sample, Past, Stable, Rose and Fell helpers in favour of manually instantiated registers.
  • Commit: amaranth-lang/amaranth@750cbbc
  • Migration Example: amaranth-lang/amaranth@28e1d28
• Uses of m.Case() with no pattern should be replaced with m.Default()
• amaranth.hdl.rec.Record will be deprecated in 0.5 and removed in 0.6
• from amaranth.vendor.lattice_ecp5 import LatticeECP5Platform becomes from amaranth.vendor import LatticeECP5Platform

There are also a number of corresponding changes happening in amaranth-soc that affect https://github.com/lambdaconcept/lambdasoc, including:

• event: migrate to lib.wiring interfaces.
• csr.bus: migrate to lib.wiring interfaces.
• wishbone.bus: migrate to lib.wiring interfaces.
• Remove log2_int
• Component metadata RFC