fix(resharding): Skip old ShardUIds in get_new_flat_storage_head() #8414

Job	Run time
Protobuf Backward Compatibility	9s
Backward Compatibility	11m 30s
Cargo Nextest (Linux)	10m 36s
Cargo Fmt	21s
Protocol Schema	13m 41s
Cargo Nextest (Linux Nightly)	10m 54s
Cargo Nextest (MacOS)	12m 3s
Database Migration	11m 38s
Genesis Changes	9m 44s
Sanity Checks	6m 50s
Style	57s
Upgradability	11m 48s
Cargo Audit	25s
Cargo Deny	32s
Cargo Clippy	9m 15s
Non-default Configuration Builds	1m 16s
Themis	41s
Unused Dependencies	6m 57s
Rust Doctests	11m 28s
Windows check for building public libraries	4m 16s
Upload Coverage	30s
Generate Coverage Artifact (unit, unit)	3m 22s
	2h 18m 53s

Provide feedback