filesystem/record should support multiple encodings of states

[jkomoros]

Detected while fixing #648.

gojsondiff has an error of diffing in certain cases.

But just switchign to josephburnett/jd doesn't feel right because a) it might also have encoding bugs, and b) there's also a legitimate need to just have full raw encoding of full states.

Make it so that records can detect their encoding of states and can save them according to it

[jkomoros]

• [x] add Matches() to the encoder interface
• [x] Use Matches in enoder() on record
• [x] Add a test that verifies that the other encoders DON'T match on our input
• [x] remove panics
• [x] Logic to auto-detect which format the file is
• [x] Have testdata examples within record package so we can test things like converting between different encodings, and so that fullPathSanityCheck can be package private. Once ChangeEncoding works, take the testdata/full.json and create a yudai derived one to verify the contents (should) be the same.
• [x] Make fullPathSanityCheck package private and test it in the main testing routines in package
• [x] Convert yudai.json to be the same actual contents as full.json so their values can be compared
• [x] DefaultStateEncoding shouldn't be a global; could conflict with different library use
• [x] Add joseph_burnett encoding
• [x] Diagnose why joseph_burnett encoding isn't working (enable test in filesystem and return it from encoding() switch table). Likely a bug in josephburnett library
• [x] In golden, we can have the default be Yudai, but if adding a state would fail to confirm, can convert to full at that point and from then on. And then every time we try to save a full we try to convert to yudai if it isn't, and only if the conversion fails do we save the full
• [x] if the jospehburnett diffs don't work in general, should we change the encoding style to be just full and diff?
• [x] Add josephburnett test in record/main_test.go (create the canonical file baesd on full.json)
• [x] ChangeEncoding()
• [x] Support full state patches
• [x] Split out State() fetching logic by the three encoding types
• [x] Switch default encoding to StateEncodingJosephBurnett
• [x] Try to compress on save automatically; if error then expand
• [x] There's a bug in memory where every so often the game when flipped to admin mode fails. Separate bug on that. No, it's recently introduced. Do a bisect and figure out what caused it and fix. No, the bug has been there for awhile, it's only switching to admin mode on first.
• [ ] rename yudai-->diff
• [ ] Then do the memory goldens.

[jkomoros]

In the end, this ended up being a full encoding (fallback) and a diff encoding (default, as long as the underlying diff library doesn't have a problem in that instance)