feat(topology/subset_properties): `locally_compact_space` instance for `Π` types (#15707)
feat(topology/subset_properties): `locally_compact_space` instance for `Π` types (#15707)

This PR adds 
- `locally_compact_space.pi` mirroring `locally_compact_space.prod` and
- `locally_compact_space.pi_finite` for finite products

Proof by: @alreadydone 



Co-authored-by: Junyan Xu <4b21477206f519dfb2e8013c7484765ce2c899c9@gmail.com>

leanprover-community/mathlib,leanprover-community/mathlib