RFC: Replace ft1/ft2 with Into<FunctionType> from tuple of TypeRow(s)

[acl-cqc]

In answer to this comment that "the ft1/ft2 helpers are quite confusing....they rather look like local variables"...

This probably doesn't make them any less confusing, indeed, it may make them more confusing, but they don't look like local variables anymore - indeed, this makes them almost disappear, so they barely look like anything anymore....

See what you think; there are a number of other variations, such as

• impl<T: Into<TypeRow>> IntoFunctionType for T i.e. dropping the unary-tuple. (We have to add a pub trait IntoFunctionType or similar to get around the foreign trait restriction but that is no big deal)
• Add pub enum FTSpec { Endo(TypeRow), InOut(TypeRow,TypeRow) } with a straightforward impl From<FTSpec> for FunctionType. The sad bit here is that FTSpec::Endo is a lot longer than ft1 and I'd really like to keep these minimal....
• Originally I'd thought of using impl Into<FTSpec> for some type FTSpec but I haven't really got anything that makes particular sense here and/or that's really different from the impl Into<FunctionType> in the PR. (Also it'd seem odd, if passing an actual FunctionType with explicit delta, to be converting FunctionType to new-spec-type and then back to FunctionType again)

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Unknown release type "RFC" found in pull request title "RFC: Replace ft1/ft2 with Into<FunctionType> from tuple of TypeRow(s)". 

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[codecov]

Codecov Report

Attention: Patch coverage is 70.83333% with 7 lines in your changes missing coverage. Please review.

Project coverage is 87.15%. Comparing base (cdc3739) to head (557e7db).

Files	Patch %	Lines
hugr-core/src/builder/dataflow.rs	40.00%	0 Missing and 3 partials ⚠️
hugr-core/src/hugr/rewrite/inline_dfg.rs	0.00%	0 Missing and 3 partials ⚠️
hugr-core/src/ops/constant.rs	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1269      +/-   ##
==========================================
- Coverage   87.15%   87.15%   -0.01%     
==========================================
  Files         103      103              
  Lines       19284    19283       -1     
  Branches    17136    17135       -1     
==========================================
- Hits        16807    16806       -1     
  Misses       1699     1699              
  Partials      778      778              

Flag	Coverage Δ
rust	86.63% <70.83%> (-0.01%)	⬇️

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[aborgna-q]

it may make them more confusing

Agree with that :P

What about just renaming the functions to ~endo_typerow and ~in_out_typerow?

[acl-cqc]

it may make them more confusing

Agree with that :P

What about just renaming the functions to ~endo_typerow and ~in_out_typerow?

They make FunctionTypes, so I could settle with endo_fn and in_out_fn ?