[python] Bump Python minimum version to 3.7

As per the RFC
https://discourse.llvm.org/t/rfc-upgrading-llvms-minimum-required-python-version/67571,
raise the minimum Python version to ensure that the Python syntax doesn't
become overly obsolete, to enable new Python feature usage, and to improve
the maintainability of CI.

llvm/CMakeLists.txt

@@ -880,8 +880,8 @@ set(LLVM_PROFDATA_FILE "" CACHE FILEPATH
   "Profiling data file to use when compiling in order to improve runtime performance.")
 
 if(LLVM_INCLUDE_TESTS)
-  # Lit test suite requires at least python 3.6
-  set(LLVM_MINIMUM_PYTHON_VERSION 3.6)
+  # All LLVM Python files should be compatible down to this minimum version.
+  set(LLVM_MINIMUM_PYTHON_VERSION 3.7)
 else()
   # FIXME: it is unknown if this is the actual minimum bound
   set(LLVM_MINIMUM_PYTHON_VERSION 3.0)

llvm/docs/GettingStarted.rst

@@ -286,15 +286,16 @@ uses the package and provides other details.
 Package                                                     Version      Notes
 =========================================================== ============ ==========================================
 `CMake <http://cmake.org/>`__                               >=3.20.0     Makefile/workspace generator
-`python <http://www.python.org/>`_                          >=3.6        Automated test suite\ :sup:`1`
+`python <http://www.python.org/>`_                          >=3.7        Automated test suite\ :sup:`1`
 `zlib <http://zlib.net>`_                                   >=1.2.3.4    Compression library\ :sup:`2`
 `GNU Make <http://savannah.gnu.org/projects/make>`_         3.79, 3.79.1 Makefile/build processor\ :sup:`3`
 =========================================================== ============ ==========================================
 
 .. note::
 
    #. Only needed if you want to run the automated test suite in the
-      ``llvm/test`` directory.
+      ``llvm/test`` directory, or if you plan to utilize any auxiliary Python
+      libraries or utilities.
    #. Optional, adds compression / uncompression capabilities to selected LLVM
       tools.
    #. Optional, you can use any other build tool supported by CMake.

llvm/docs/GettingStartedVS.rst

@@ -55,7 +55,7 @@ Visual Studio 2019 so separate installation is not required. If you do install
 CMake separately, Visual Studio 2022 will require CMake Version 3.21 or later.
 
 If you would like to run the LLVM tests you will need `Python
-<http://www.python.org/>`_. Version 3.6 and newer are known to work. You can
+<http://www.python.org/>`_. Version 3.7 and newer are known to work. You can
 install Python with Visual Studio 2019, from the Microsoft store or from
 the `Python web site <http://www.python.org/>`_. We recommend the latter since it
 allows you to adjust installation options.

llvm/docs/TestingGuide.rst

@@ -23,7 +23,7 @@ Requirements
 ============
 
 In order to use the LLVM testing infrastructure, you will need all of the
-software required to build LLVM, as well as `Python <http://python.org>`_ 3.6 or
+software required to build LLVM, as well as `Python <http://python.org>`_ 3.7 or
 later.
 
 LLVM Testing Infrastructure Organization