Adds test for AppendVec::get_account_sizes() (#2081) #481

Job	Run time
cargo-test-sbf (token/program)	9m 21s
check	3m 55s
cargo-test-sbf (instruction-padding/program, token/program-2022, token/program-2022-test)	15m 14s
test (token/cli, token/program, token/program-2022, associated-token-account/program, instruction...	18m 31s
cargo-test-sbf (associated-token-account/program, associated-token-account/program-test)	8m 31s
test (single-pool/cli, single-pool/program)	17m 52s
cargo-test-sbf (token-upgrade/program)	8m 23s
test (token-upgrade/cli, token-upgrade/program)	16m 8s
cargo-test-sbf (feature-proposal/program)	7m 34s
cargo-test-sbf (governance/addin-mock/program, governance/program)	11m 35s
cargo-test-sbf (memo/program)	9m 28s
cargo-test-sbf (name-service/program)	7m 25s
cargo-test-sbf (stake-pool/program)	12m 56s
cargo-test-sbf (single-pool/program)	10m 18s
	2h 37m 11s

Provide feedback