Improve variable conversion & comparison handling as well as CMake version compatibility

[3manifold]

Importing quill source code as part of a larger project can reveal points of improvement mainly pointed out by inherited compiler flags. Fixes include:

• Tolerate float comparison when using equality operator.

# error
comparing floating point with == or != is unsafe [-Werror,-Wfloat-equal]

• Improve implicit conversion to avoid lose of precision (hopefully multiplication result falls in the original author's error tolerance intention).

# warning
  implicit conversion from 'const integer_type' (aka 'const unsigned long') to 'double' may lose precision [-Werror,-Wimplicit-int-float-conversion]

• Modern CMake versions (e.g. 3.31.5) can reveal obsolete CMake policy incompatibility. Changing minimum version to 3.10 alleviates these warnings. Worth noting that current version 3.8 dates back to 2017.

# warning message
CMake Deprecation Warning at extern/quill/CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 3.10 will be removed from a future version of
  CMake.
<...>

[odygrd]

Hey, thanks for the PR. Which line of code is giving you this warning ? And on which compiler? I would prefer to fix it rather than silencing it

‘comparing floating point with == or != is unsafe [-Werror,-Wfloat-equal]’

[3manifold]

Hi, it is clang 19.1.7 and line if (value == 0). The code will fail to build if one uses -Wfloat-equal.

[odygrd]

Thanks, I have silenced the warning in this PR, so let's not add the Wfloat-equal flag please

#672

if we add a compilation flag to an interface target that flag or definition will propagate to all translation units that include the headers from that interface target