Add support for Python 3.10 (#29581)

* Add support for Python 3.10

* Update unit-tests to use 3.10

* Update Getting started section of the docs

* Update bootstrap action

lib/spack/docs/getting_started.rst

@@ -149,27 +149,28 @@ Spack fall back to bootstrapping from sources:
 
 .. code-block:: console
 
-   $ spack bootstrap untrust github-actions
-   ==> "github-actions" is now untrusted and will not be used for bootstrapping
+   $ spack bootstrap untrust github-actions-v0.2
+   ==> "github-actions-v0.2" is now untrusted and will not be used for bootstrapping
 
 You can verify that the new settings are effective with:
 
 .. code-block:: console
 
    $ spack bootstrap list
-   Name: github-actions UNTRUSTED
+   Name: github-actions-v0.2 UNTRUSTED
 
      Type: buildcache
 
      Info:
-       url: https://mirror.spack.io/bootstrap/github-actions/v0.1
-       homepage: https://github.com/alalazo/spack-bootstrap-mirrors
-       releases: https://github.com/alalazo/spack-bootstrap-mirrors/releases
+       url: https://mirror.spack.io/bootstrap/github-actions/v0.2
+       homepage: https://github.com/spack/spack-bootstrap-mirrors
+       releases: https://github.com/spack/spack-bootstrap-mirrors/releases
 
      Description:
        Buildcache generated from a public workflow using Github Actions.
        The sha256 checksum of binaries is checked before installation.
 
+   [ ... ]
 
    Name: spack-install TRUSTED
 

lib/spack/docs/tables/system_prerequisites.csv

@@ -1,5 +1,5 @@
 Name, Supported Versions, Notes, Requirement Reason
-Python, 2.7/3.5-3.9, , Interpreter for Spack
+Python, 2.7/3.5-3.10, , Interpreter for Spack
 C/C++ Compilers, , , Building software
 make, , , Build software
 patch, , , Build software

lib/spack/spack/test/llnl/util/lock.py

@@ -570,7 +570,7 @@ def test_write_lock_timeout_with_multiple_readers_3_2(lock_path):
 def test_write_lock_timeout_with_multiple_readers_2_1_ranges(lock_path):
     multiproc_test(
         AcquireRead(lock_path, 0, 10),
-        AcquireRead(lock_path, 0.5, 10),
+        AcquireRead(lock_path, 2, 10),
         TimeoutWrite(lock_path, 5, 5))