Remove the spack.architecture module (#25986)

The `spack.architecture` module contains an `Arch` class that is very similar to `spack.spec.ArchSpec` but points to platform, operating system and target objects rather than "names". There's a TODO in the class since 2016:

https://github.com/spack/spack/blob/abb0f6e27c45758c37fd45d663214b86413fb4f6/lib/spack/spack/architecture.py#L70-L75

and this PR basically addresses that. Since there are just a few places where the `Arch` class was used, here we query the relevant platform objects where they are needed directly from `spack.platforms`. This permits to clean the code from vestigial logic.

Modifications:
- [x] Remove the `spack.architecture` module and replace its use by `spack.platforms`
- [x] Remove unneeded tests

1 files changed, 2 insertions, 2 deletions

diff --git a/var/spack/repos/builtin/packages/gcc/package.py b/var/spack/repos/builtin/packages/gcc/package.py
index 307cd75404..d8772b215e 100644
--- a/var/spack/repos/builtin/packages/gcc/package.py
+++ b/var/spack/repos/builtin/packages/gcc/package.py
@@ -10,7 +10,7 @@ import sys
 
 import llnl.util.tty as tty
 
-import spack.architecture
+import spack.platforms
 import spack.util.executable
 from spack.operating_systems.mac_os import macos_sdk_path, macos_version
 
@@ -324,7 +324,7 @@ class Gcc(AutotoolsPackage, GNUMirrorPackage):
                 continue
             # Filter out links in favor of real executables on
             # all systems but Cray
-            host_platform = str(spack.architecture.platform())
+            host_platform = str(spack.platforms.host())
             if os.path.islink(exe) and host_platform != 'cray':
                 continue