This updates the tests submodule to the London fork tests, and
also updates the test runner to support the new EIP-1559 fields in
test JSON.

Fixes #15777 because null is now allowed for hexutil.Bytes.

Tests are now included as a submodule. This should make updating easier
and removes ~60MB of JSON data from the working copy.

State tests are replaced by General State Tests, which run the same test
with multiple fork configurations.

With the new test runner, consensus tests are run as subtests by walking
json files. Many hex issues have been fixed upstream since the last
update and most custom parsing code is replaced by existing JSON hex
types. Tests can now be marked as 'expected failures', ensuring that
fixes for those tests will trigger an update to test configuration. The
new test runner also supports parallel execution and the -short flag.

* Makefile: fix devtools target

* core: regenerate genesis marshaling with fjl/gencodec@cbfa5be5a8a8

* core/types: regenerate marshaling methods with fjl/gencodec@cbfa5be5a8a8

* core/types: add "hash" to JSON headers

Regenerated with fjl/gencodec@1a75a2161009
Also add ,omitempty to optional GenesisAccount fields.

This commit solves several issues concerning the genesis block:

* Genesis/ChainConfig loading was handled by cmd/geth code. This left
  library users in the cold. They could specify a JSON-encoded
  string and overwrite the config, but didn't get any of the additional
  checks performed by geth.
* Decoding and writing of genesis JSON was conflated in
  WriteGenesisBlock. This made it a lot harder to embed the genesis
  block into the forthcoming config file loader. This commit changes
  things so there is a single Genesis type that represents genesis
  blocks. All uses of Write*Genesis* are changed to use the new type
  instead.
* If the chain config supplied by the user was incompatible with the
  current chain (i.e. the chain had already advanced beyond a scheduled
  fork), it got overwritten. This is not an issue in practice because
  previous forks have always had the highest total difficulty. It might
  matter in the future though. The new code reverts the local chain to
  the point of the fork when upgrading configuration.

The change to genesis block data removes compression library
dependencies from package core.