perf: reduce DevExtension discovery max_depth from 3 to 2

The _collect() helper in DevExtension.get_all() recursively walks directories
to find *.egg-info markers. A max_depth of 3 is excessive since standard dev
extension layouts place .egg-info at depth 1 (pip install -e) or depth 2
(azure-cli-extensions repo: src/<ext_name>/*.egg-info).

Reducing to max_depth=2 eliminates an entire level of recursive os.path.isdir(),
glob(), and os.listdir() calls, saving ~30-50 ms on Windows when DEV_EXTENSION_SOURCES
is configured.

Author: ReaNAiveD

src/azure-cli-core/azure/cli/core/extension/__init__.py

@@ -268,7 +268,7 @@ def _collect(path, depth=0, max_depth=3):
                 for item in os.listdir(path):
                     _collect(os.path.join(path, item), depth + 1, max_depth)
         for source in DEV_EXTENSION_SOURCES:
-            _collect(source)
+            _collect(source, max_depth=2)
         # https://docs.python.org/3/library/os.html#os.listdir, listdir is in arbitrary order.
         # Sort the extensions by name to support overwrite extension feature: https://github.com/Azure/azure-cli/issues/25782.
         exts.sort(key=lambda ext: ext.name)