crate_universe: Enable modext isolation.

This should allow us to build our python and ruby
code independently - in particular, we can now do shallow
checkouts of one without the other.
Previously, the modext introduced cross-dependency.
This also reduces the amount of work we do in the
crate universe processing for the other language, even
though it's unused.

.bazelrc

@@ -24,5 +24,6 @@ common --registry=file:///%workspace%/misc/bazel/registry
 common --registry=https://bcr.bazel.build
 
 common --@rules_dotnet//dotnet/settings:strict_deps=false
+common --experimental_isolated_extension_usages
 
 try-import %workspace%/local.bazelrc

.bazelrc.internal

@@ -8,3 +8,4 @@ common --registry=https://bcr.bazel.build
 # its implementation packages without providing any code itself.
 # We either can depend on internal implementation details, or turn of strict deps.
 common --@rules_dotnet//dotnet/settings:strict_deps=false
+common --experimental_isolated_extension_usages

MODULE.bazel

@@ -30,27 +30,35 @@ bazel_dep(name = "rules_rust", version = "0.46.0")
 
 bazel_dep(name = "buildifier_prebuilt", version = "6.4.0", dev_dependency = True)
 
-crate = use_extension(
+crate_py = use_extension(
     "@rules_rust//crate_universe:extension.bzl",
     "crate",
+    isolate = True,
 )
-crate.from_cargo(
+crate_py.from_cargo(
     name = "py_deps",
     cargo_lockfile = "//python/extractor/tsg-python:Cargo.lock",
     manifests = [
         "//python/extractor/tsg-python:Cargo.toml",
         "//python/extractor/tsg-python/tsp:Cargo.toml",
     ],
 )
-crate.from_cargo(
+use_repo(crate_py, "py_deps")
+
+crate_ruby = use_extension(
+    "@rules_rust//crate_universe:extension.bzl",
+    "crate",
+    isolate = True,
+)
+crate_ruby.from_cargo(
     name = "ruby_deps",
     cargo_lockfile = "//ruby/extractor:Cargo.lock",
     manifests = [
         "//ruby/extractor:Cargo.toml",
         "//ruby/extractor/codeql-extractor-fake-crate:Cargo.toml",
     ],
 )
-use_repo(crate, "py_deps", "ruby_deps")
+use_repo(crate_ruby, "ruby_deps")
 
 dotnet = use_extension("@rules_dotnet//dotnet:extensions.bzl", "dotnet")
 dotnet.toolchain(dotnet_version = "8.0.101")