[FIRRTLToHW] Fix crash when lowering instance_choice with clock outputs

[seldridge]

When lowering instance_choice operations with clock-typed output ports,
the code was attempting to create sv.wire operations with !seq.clock as
the element type. However, !seq.clock is not a valid element type for
hw.inout, causing an assertion failure.

The fix follows the same pattern used for XMR operations: use i1 wires
instead of !seq.clock wires, and convert to/from clock when reading/
writing:

• When creating wires for clock outputs, use i1 type
• When reading from the wire (for the result value), convert i1 to clock
  using seq.to_clock
• When writing to the wire (from instance outputs), convert clock to i1
  using seq.from_clock

This allows instance_choice to work correctly with clock-typed ports
while respecting the type constraints of hw.inout.

Fixes a crash with the error:
error: invalid element for hw.inout type '!seq.clock'
Assertion failed: (succeeded(ConcreteT::verifyInvariants(...)))

AI-assisted-by: Augment (Claude Sonnet 4.5)
Signed-off-by: Schuyler Eldridge schuyler.eldridge@sifive.com

This is DRAFT as I have not reviewed it yet!

[seldridge]

There should be a better fix than this once @uenoku finishes instance choice support. I'll leave this open for now.

[uenoku]

As we don't pursue the direction of #9900 and #9948 for now, we need to fix this even when we switched to generate statement.

[uenoku]

LGTM