add support for foreach target

[skshetry]

• checkout¹
• commit²
• dag
• fetch¹
• freeze/unfreeze⁴
• pull¹
• push¹
• remove³
• status
• exp run (already supported)
• repro (already supported)
• stage list (already supported)

Closes #7323.

Notes:

1. checkout might fail if any of the hash_info from the foreach group is missing (it'll still checkout). Same with pull/push/fetch.
2. commit might fail if the workspace has any output missing from the foreach group (this is a bit annoying).
3. remove is not supported as it needs to modify templated dvc.yaml file, which we don't support yet. We can skip it for now. Internally in dvc, we don't have a "foreach group" to remove, it's compiled away, so we only know about individual stages that it generates. So removing a definition for that foreach group requires custom logic to handle foreach group, and then need to imitate whatever behaviour we have for remove, i.e unprotect from cache, remove from dvc.lock and dvc.yaml, remove .gitignore entries, etc.
4. freeze/unfreeze is similar to 3. We don't modify parameterized stages and would require custom handling for that. We try not to modify dvc.yaml as much as possible.

Related: #7462, #7385

[dberenbaum]

LGTM! The edge cases you mention are fine to deprioritize.