Enforce constraints during install_package_deps

[masenf]

Create a constraints file based on the listed or installed deps and use it during install_package_deps to ensure the package dependencies do not override the environment's dependencies.

Adds new config keys:

• constrain_package_deps - chicken switch to go back to the legacy behavior of allowing the package deps to override the testenv deps
• use_frozen_constraints - a more strict mode, enforced that the package deps do not conflict in any way with the set of packages installed by deps

Fix #2386

Thanks for contribution

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• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation

[gaborbernat]

msg =  f"constraint options changed: old={old.get('constraint_options')} new={constraint_options}"
raise Recreate(msg)

would save you a line here 🤔

[masenf]

i thought so too, but black disagreed

diff --git a/src/tox/tox_env/python/pip/pip_install.py b/src/tox/tox_env/python/pip/pip_install.py
index 640c1356..e608c2b7 100644
--- a/src/tox/tox_env/python/pip/pip_install.py
+++ b/src/tox/tox_env/python/pip/pip_install.py
@@ -134,7 +134,9 @@ class Pip(Installer[Python]):
                     if missing_requirement:
                         raise Recreate(f"requirements removed: {' '.join(missing_requirement)}")
                     if old.get("constraint_options") != constraint_options:
-                        msg = f"constraint options changed: old={old.get('constraint_options')} new={constraint_options}"
+                        msg = (
+                            f"constraint options changed: old={old.get('constraint_options')} new={constraint_options}"
+                        )
                         raise Recreate(msg)
                 args = arguments.as_root_args
                 if args:  # pragma: no branch

[masenf]

i ended up making it a little cleaner by assigning old_constraint_options = old.get("constraint_options")