Discover workspaces without using them in resolution (#3585)

Add minimal support for workspace discovery, only used for determining
paths in the bluejay commands.

We can now discover the workspace structure, namely that the
`pyproject.toml` of a package belongs to a workspace `pyproject.toml`
with members and exclusion. The globbing logic is inspired by cargo. We
don't resolve `workspace = true` metadata declarations yet.

scripts/workspaces/albatross-in-example/check_installed_albatross.py

@@ -0,0 +1,11 @@
+from albatross import fly
+
+try:
+    from bird_feeder import use
+
+    raise RuntimeError("bird-feeder installed")
+except ModuleNotFoundError:
+    pass
+
+fly()
+print("Success")

scripts/workspaces/albatross-in-example/examples/bird-feeder/check_installed_bird_feeder.py

@@ -0,0 +1,10 @@
+from bird_feeder import use
+
+try:
+    from albatross import fly
+
+    raise RuntimeError("albatross installed")
+except ModuleNotFoundError:
+    pass
+
+print("Success")

scripts/workspaces/albatross-in-example/examples/bird-feeder/pyproject.toml

@@ -0,0 +1,8 @@
+[project]
+name = "bird-feeder"
+version = "1.0.0"
+dependencies = ["anyio>=4.3.0,<5"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"

scripts/workspaces/albatross-in-example/examples/bird-feeder/src/bird_feeder/__init__.py

@@ -0,0 +1,5 @@
+import anyio
+
+
+def use():
+    print("squirrel")

scripts/workspaces/albatross-in-example/pyproject.toml

@@ -0,0 +1,8 @@
+[project]
+name = "albatross"
+version = "0.1.0"
+dependencies = ["tqdm>=4,<5"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"

scripts/workspaces/albatross-in-example/src/albatross/__init__.py

@@ -0,0 +1,9 @@
+import tqdm
+
+
+def fly():
+    pass
+
+
+if __name__ == '__main__':
+    print("Caw")