Improve CMake build

[hcho3]

• Add option to hide C++ symbols
• Add option to "use system libtreelite.so." That is, if libtreelite.so is available in sys.prefix (e.g. Conda env), do not build another copy of libtreelite.so for the Python package. Previously, Conda's Treelite package would end up installing two copies of libtreelite.so.
• Add option to select dynamic or static MSVC runtime
• Use CMake's built-in directive CMAKE_MSVC_RUNTIME_LIBRARY instead of manually manipulating compiler flags. This helps us avoid cryptic CMake errors when using Treelite as a CMake sub-directory.
• Prefix a few options with Treelite_ to make it easy for other downstream projects to use these options.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.70 ⚠️

Comparison is base (9087997) 85.34% compared to head (7382702) 84.65%.

❗ Current head 7382702 differs from pull request most recent head d76918f. Consider uploading reports for the commit d76918f to get more accurate results

Additional details and impacted files

@@              Coverage Diff               @@
##             mainline     #484      +/-   ##
==============================================
- Coverage       85.34%   84.65%   -0.70%     
  Complexity         42       42              
==============================================
  Files             112      111       -1     
  Lines            9914     8849    -1065     
  Branches          617       40     -577     
==============================================
- Hits             8461     7491     -970     
+ Misses           1430     1335      -95     
  Partials           23       23              

see 68 files with indirect coverage changes

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