[stdlib] Speed up the FixedPointConversion tests

[benrimmington]

Follow-up to: #36205

• Added python3 compatibility.
• Added .forEach parameterized code.
• Removed long_test requirements.
• Tested on macOS and watchOS simulator.

utils/run-test \
  --build-dir ../build/Ninja-RelWithDebInfoAssert \
  --subset all \
  --target macosx-x86_64 \
  --verbose \
  validation-test/stdlib/FixedPointConversion/*.swift

********************

Testing Time: 16.77s (old), 13.82s (new)
  Unsupported: 20
  Passed     : 20

utils/run-test \
  --build-dir ../build/Ninja-RelWithDebInfoAssert \
  --subset all \
  --target watchsimulator-i386 \
  --verbose \
  validation-test/stdlib/FixedPointConversion/*.swift

********************

Testing Time: 60.25s (old), 14.37s (new)
  Unsupported: 20
  Passed     : 20

[benrimmington]

@swift-ci Please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - ac5ae7e361b4657931ab6088f0b5df972ce827c8

[benrimmington]

<unknown>:0: error: module file '/home/buildnode/jenkins/workspace/swift-PR-Linux/branch-main/buildbot_linux/foundation-linux-x86_64/module-cache/32AAGSXEGLMNI/SwiftShims-RRC23Z1R7B4K.pcm' is out of date and needs to be rebuilt: signature mismatch
<unknown>:0: note: imported by module 'SwiftOverlayShims' in '/home/buildnode/jenkins/workspace/swift-PR-Linux/branch-main/buildbot_linux/foundation-linux-x86_64/module-cache/32AAGSXEGLMNI/SwiftOverlayShims-RRC23Z1R7B4K.pcm'
/home/buildnode/jenkins/workspace/swift-PR-Linux/branch-main/swift-corelibs-foundation/Sources/Foundation/Data.swift:25:8: error: missing required module 'SwiftOverlayShims'
import Glibc
       ^
ninja: build stopped: subcommand failed.

[swift-ci]

Build failed
Swift Test OS X Platform
Git Sha - ac5ae7e361b4657931ab6088f0b5df972ce827c8

[benrimmington]

Unexpectedly Passed Tests (1):
  lldb-shell :: Stepper/TestSwiftBenchmarkOnone.1.test

[benrimmington]

@swift-ci Please test

[benrimmington]

@swift-ci Please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - a315221

[benrimmington]

Failed Tests (1):
  Swift(linux-x86_64) :: Driver/static-stdlib-linux.swift

[benrimmington]

@swift-ci Please test Linux platform