Refactors the ManifestReader implementation to support advanced data skipping
and projection pushdown, and adds full test coverage ported from the Java implementation.

Implementation Changes:

• Consolidate ManifestReader logic: Move implementation from manifest_reader_internal.cc
  to manifest_reader.cc and remove the obsolete internal class.
• Fluent API: Add Select(), FilterPartitions(), and FilterRows() to support
  column projection and expression-based filtering (partition & metrics).
• Optimization: Support lazy initialization of the underlying Avro reader.
• ManifestEntry: Update schema handling to support reading specific columns and stats.

Test Coverage:

• Add manifest_reader_test.cc: Ports TestManifestReader from Java, covering:
  • Basic reading and partition filtering.
  • V2/V3 specific features: Delete Files and Deletion Vectors (DVs).
  • Invalid usage validation (missing snapshot ID).
• Add manifest_reader_stats_test.cc: Ports TestManifestReaderStats, verifying:
  • Metrics projection logic (stats columns included/dropped based on filter/select).
  • Exact match of stats parsing against expected values.
• Parameterized Testing: All tests run against Format Versions 1, 2, and 3 to ensure cross-version compatibility.