Cardano Updates

Signed-off-by: Chris Gianelloni <[email protected]>

* add 'cardano_' prefix to stability threshold environment variable name
* improve consistency and clarity of environment variable naming

feat(mithril-stm): add reproducible benchmarks for StmCertificateCircuit

cabal v2-build prepends `<unit>/bin/` to PATH when invoking ghc for
any package whose `build-tool-depends:` refers to that unit.  In our
cross-compilation setup we compose the build-tool's cross-target
`targetSlice` into the slice's cabal-store (so cabal recognises the
unit-id plan-nix recorded as "already installed") — but that means
the binary cabal prepends to PATH is for the cross-target arch.
ghc's `-pgmF hspec-discover` PATH lookup then resolves to the
cross-arch binary and `posix_spawnp` returns ENOEXEC ("Exec format
error") on the build host.

`withProgFlags` already passes
`--configure-option=--with-<tool>=<buildSlice>/bin/<tool>` so Setup
configure picks up the build-platform variant — but cabal v2-build's
own PATH-prepend for ghc preprocessor invocations bypasses that.

After lndir-composing the cabal-store, walk
`<storeDir>/<ghc>/*-e-<name>-*/bin/<name>` for each transitive
build-tool entry and replace the symlink with a copy of
`${buildSlice}/bin/${name}` (the build-platform binary).  The
cross-target unit-id directory stays intact (so cabal's solver
still recognises it), but the executable inside is one that
actually runs on the build machine.

Native builds have an empty `buildToolBinOverlays`, so the overlay
block emits an empty string and other slices' drv hashes are
unchanged.

Confirmed:
  * x86_64-linux armv7a-android cabal-22.run (was failing with
    `hspec-discover: posix_spawnp: invalid argument (Exec format error)`)
  * x86_64-linux musl64 githash.run, th-dlls.build
  * x86_64-linux native with-packages.run
  * x86_64-linux armv7a-android c-ffi.run

* add utility function `parsePositiveBigIntEnv`
* change unique pools stability threshold to use environment variable
* update local gateway setup to set stability threshold environment variable

Signed-off-by: Akhil Repala <[email protected]>

* add logic to ensure gateway and its dependencies are built
* build proto-types and specific cardano-ibc packages if not already built
* install gateway dependencies and build the gateway before starting

* add conditional installation of gateway npm dependencies
* prevent script execution failures due to missing dependencies