add derive(Serialize, Deserialize) to DecompressorOxide

[dishmaker]

Fixes

• DecompressorOxide: Serialize state with serde #165
• derive(Serialize) state: Fsm vs AsyncSeek bearcove/rc-zip#99

I know this PR will not be merged, but it proves that state saving is actually possible!

Entire DecompressorOxide state compresses into only 356 bytes, for simple test case.

partial read len=32768
save at in_pos=11729
[miniz_oxide/tests/test_serde.rs:57:5] decompressor_state_msgpack.len() = 11824
[miniz_oxide/tests/test_serde.rs:58:5] decompressor_state_compressed.len() = 356
resume at in_pos=11729

So fast-seekable zip files are possible 😄

[oyvindln]

Could you leave leave the black_box change out of this PR? I would like to evaluate that separately.

I think adding a serde feature could be fine if there is a use for it though I would prefer if it's not enabled by default. Is it also possible to only enable the rmp_serde dev dependency conditionally?