Core: Add snapshotTransformer API for TableMetadata

[singhpk234]

About the change

Introduces a transformSnapshots API in the TableMetadata, one use case which will be helpful is snapshot summary contains information like total files / total-records etc and when partition summary is enabled it contains partition summary which is a sensitive information incase the table is protected against FGAC specially Row Access Policy, this essentially will help in dropping the snapshot summary by the RESTCatlaog before the table metadata is being sent to the being sent to the client (untrusted) as part of LoadTable response.
Never the less dropping the summary from snapshot obj can reduce the size transfer cost.

Testing

unit tests for w/wo lazy loading

[singhpk234]

I was talking to @stevenzwu, he suggested a nice alternative here inspired by StructProjection adding it here for broder forum, techinically indeed its a projection

class TableMetadataProjection {

  TableMetadata create(TableMetadata metadata, Function<Snapshot, Snapshot> transformer) {
    new SnapshotTransformer(metadata.())
  }

  private static class SnapshotTransformer extends TableMetadata {
    @Override
    public List<Snapshot> snapshots() {
      List<Snapshot> s = super.snapshot()
      // apply the tranform on s ?
    }
  }

In this approach we will need to make all the members getters, they can be package private for sure ! we additionally would want to serialize the tranformer too if we want to send this back as part of loadTableResponse ?