Pallet-anchors: replace Vec storage by BoundedVec

[lemunozm]

Description

Replace Vec storage with BoundedVec in pallet-anchors to be prepared for Weights V2

Related to: #897

Changes and Descriptions

Modify Vec types found in the pallet-anchors storages.

Type of change

• Bug fix (non-breaking change which fixes an issue). In this case, a future issue.

How Has This Been Tested?

cargo test -p pallet-anchors
cargo test --workspace --release --features test-benchmarks,try-runtime
cargo run --features runtime-benchmarks benchmark pallet --pallet="pallet-anchors" --chain="altair-dev" --extrinsic="*"

Checklist:

• I have performed a self-review of my code
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• I rebased on the latest parachain branch

[mustermeiszer]

LGTM!