[PR] AVRO-4343: [perl] Fix broken decoder skip path used in schema resolution [avro]

["iemejia (via GitHub)" <gi...@apache.org>]

iemejia opened a new pull request, #3947:
URL: https://github.com/apache/avro/pull/3947

   ## What
   
   Fixes the Perl `BinaryDecoder` **skip path**, which is exercised during schema resolution whenever the writer's record contains a field that is absent from the reader's schema (`decode_record` → `skip`). Three related defects, present since the initial Perl implementation (AVRO-974):
   
   1. **Absolute seek → silent data corruption.** `skip_bytes`/`skip_string`/`skip_fixed` did `$reader->seek($size, 0)` — whence `0` is `SEEK_SET` (absolute) rather than `SEEK_CUR`. Skipping a bytes/string/fixed field repositioned the reader to absolute offset `$size`, corrupting every subsequent field. (Masked in the existing test only because its skipped field was the last one.)
   2. **Crash when skipping an array/map field.** `skip_array`/`skip_map` invoked `skip_block(...)` as a plain sub, so `shift`ing `$class` misaligned `$reader` and the content callback, dying with *"Can't call method \"read\" on unblessed reference"*.
   3. **Broken negative-block-count handling.** `skip_block` seeked to a negative absolute offset and re-looped via `next` without re-reading the block count.
   
   ## Fix
   
   - Use relative (`SEEK_CUR`) skips in `skip_bytes`/`skip_string`/`skip_fixed`.
   - Reject negative bytes lengths and negative block sizes with `Avro::Schema::Error::Parse`.
   - Invoke `skip_block` as a method (`$class->skip_block`), fixing the argument alignment.
   - Handle negative block counts the same way as `decode_array`/`decode_map`: take the absolute value and consume the following block-size long.
   
   ## Tests
   
   Adds regression tests to `t/03_bin_decode.t` covering resolution that skips: a non-trailing `bytes` field, an `array` field, a `map` field, an `array` encoded with a **negative block count**, and rejection of a negative bytes length. Full existing Perl suite still passes (the pre-existing `04_datafile.t` failure is unrelated — a missing `IO::Compress` dependency).
   
   JIRA: https://issues.apache.org/jira/browse/AVRO-4343


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