ParquetMetaData memory size is not reported accurately when encryption is enabled #8472
Description
Describe the bug
While working on #8470 I noticed that the API to report memory usage when encryption was used undercounts the actual memory used
ParquetMetaData::memory_size is used for memory accounting for in memory parquet caches, and thus should be accurate
To Reproduce
Specifically this function
arrow-rs/parquet/src/file/metadata/mod.rs
Lines 281 to 286 in b8ae8e0
Does not account for the heap allocations in the file_decryptor field:
arrow-rs/parquet/src/file/metadata/mod.rs
Line 191 in b8ae8e0
Expected behavior
ParquetMetaData::memory_size should report its actually heap allocation size (by implementing the HeapSize trait for FileDecryptor and all its subfields
Additional context