* feat: add (re)delegation getters (#11596)
### Description
This PR adds general helper functions to the `x/staking` module that are used in the Evmos `x/vesting` module and originated from Agoric's custom staking module implementation https://github.com/agoric-labs/cosmos-sdk/blob/4085-true-vesting/x/staking/keeper/delegation.go.
- `GetDelegatorUnbonding`
- `GetDelegatorBonded`
- `IterateDelegatorUnbondingDelegations`
- `IterateDelegatorDelegations`
- `IterateDelegatorRedelegations`
(cherry picked from commit b8270fc9ba)
# Conflicts:
# CHANGELOG.md
# x/staking/keeper/delegation.go
* fix RemoveDelegation method conflict
* fix CHANGELOG conflict
* add new PR in CHANGELOG
Co-authored-by: Daniel Burckhardt <daniel.m.burckhardt@gmail.com>