Rename p2300 to stdexec (#33099)

* Rename p2300 package after renaming PR merged in stdexec

https://github.com/NVIDIA/stdexec/pull/622

* Adapt pika to depend on stdexec

var/spack/repos/builtin/packages/pika/package.py

@@ -94,7 +94,7 @@ class Pika(CMakePackage, CudaPackage, ROCmPackage):
     depends_on("hip@5.2:", when="@0.8: +rocm")
     depends_on("hipblas", when="@:0.8 +rocm")
     depends_on("mpi", when="+mpi")
-    depends_on("p2300", when="+p2300")
+    depends_on("stdexec", when="+p2300")
     depends_on("rocblas", when="+rocm")
     depends_on("rocsolver", when="@0.5: +rocm")
     depends_on("tracy-client", when="+tracy")

var/spack/repos/builtin/packages/stdexec/package.py

@@ -6,7 +6,7 @@
 from spack.package import *
 
 
-class P2300(CMakePackage):
+class Stdexec(CMakePackage):
     """The proposed C++ framework for asynchronous and parallel programming."""
 
     homepage = "https://github.com/NVIDIA/stdexec"