Set a maximum test run-time of 20 minutes to:
- fail faster
- avoid wasting CI resources
- set a bound on the test time (if tests take longer than 20 minutes we
  need to invest in parallelizing them...)

Timeout looks like:

    -- Tests exited non-zero: Process terminated due to timeout
    -- No output to stderr.
    CMake Error at /…/neovim/cmake/RunTests.cmake:86
    (message):
      functional tests failed with error: Process terminated due to timeout

`find_package(Foo ...)` expects to find a file FindFoo.cmake and the
resulting variables to be named `Foo_...`.  If those don't all match up,
then the detection does not work properly.

Closes #13262

fixup! bundle: move tree-sitter as a bundled dep

fixup! bundle: move tree-sitter as a bundled dep

Lua 5.4 is out, and will be shipped with Fedora 33.

Problem:  On Windows with the MSVC build, gettext-translation
          "Questa è già la" displays as "Questa <e8> gi<e0> la".
Solution: Fix iconv detection iconv when building gettext.
          So HAVE_ICONV is correctly defined when building nvim.

* fix gettext mb chars on MSVC
* fix libintl detection failure on MSVC

fixes #11749

This avoids invoking CMake after a new commit, which might take 15s on
some systems.

Skipped on CMake < 3.2.0 (missing BYPRODUCTS support).

Co-Authored-By: Justin M. Keyes <justinkz@gmail.com>

Also update doc.