Fix pushLong() issue in pickler. (#28057)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28057
For pushLong() in Pickler, it looks like we only use for a single use case, with a 10-byte value.
We were handling > 256 bytes incorrectly, by using a LONG4 opcode (expecting 4-byte length), but pushing 8 bytes. We could harden this handling, but rather than improve codepaths that we never expect to use, this change simply removes the incorrect codepath and adds and assert.
ghstack-source-id: 92048325
Test Plan: buck test mode/dev-nosan caffe2/test/...
Differential Revision: D17934174
fbshipit-source-id: ecc1ca37dbcc87151fc5bf2ffb6b05dff91d3667
