feat(venv): Make the venv linking strategy configurable

[arrdem]

Add a config_setting allowing users to toggle the default venv strategy so that users have to explicitly opt into the new-style static venv.

Mitigates #696

Changes are visible to end-users: yes

• Searched for relevant documentation and updated as needed: yes
• Breaking change (forces users to change their own code or config): yes
• Suggested release notes appear below: yes

Test plan

• Manual testing; please provide instructions so we can reproduce:

TODO

[aspect-workflows]

test-os:linux-bzl:8 (Test)

All tests were cache hits

38 tests (100.0%) were fully cached saving 51s.

---

test-os:linux-bzl:latest (Test)

All tests were cache hits

38 tests (100.0%) were fully cached saving 51s.

---

test-os:linux-bzl:8 (Test)

e2e

All tests were cache hits

14 tests (100.0%) were fully cached saving 10s.

---

test-os:linux-bzl:latest (Test)

e2e

All tests were cache hits

14 tests (100.0%) were fully cached saving 10s.

---

test-os:linux-bzl:8 (Test)

examples/uv_pip_compile

All tests were cache hits

1 test (100.0%) was fully cached saving 335ms.

---

test-os:linux-bzl:latest (Test)

examples/uv_pip_compile

All tests were cache hits

1 test (100.0%) was fully cached saving 335ms.