Added get_keys_for_plot daemon server API

[ChiaMineJP]

This PR is a partial PR cut from cmj.plot2_0 branch.

[arvidn]

looks reasonable. do you think it's realistic to have tests? I don't think we have any infrastructure for it

[coveralls-official]

Pull Request Test Coverage Report for Build 5586985052

• 82 of 82 (100.0%) changed or added relevant lines in 3 files are covered.
• 1192 unchanged lines in 40 files lost coverage.
• Overall coverage increased (+0.2%) to 87.65%

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Files with Coverage Reduction	New Missed Lines	%
chia/cmds/chia.py	1	80.81%
chia/full_node/bundle_tools.py	1	98.59%
tests/core/test_full_node_rpc.py	1	99.69%
tests/build-job-matrix.py	2	89.9%
tests/wallet/db_wallet/test_dl_offers.py	2	99.19%
chia/util/errors.py	3	98.76%
chia/wallet/wallet_node.py	3	86.43%
chia/wallet/wallet_state_manager.py	3	95.23%
tests/wallet/cat_wallet/test_trades.py	3	99.36%
chia/wallet/util/puzzle_compression.py	4	92.98%

Totals
Change from base Build 5551480313:	0.2%
Covered Lines:	80725
Relevant Lines:	91988

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💛 - Coveralls

[emlowe]

This seems fine, but I don't like the name that much get_keys_for_plot would suggest to me that I provide a PLOT as a parameter to the call and get back the keys used for the plot.

However, I believe this call is returning the farmer and pool public keys for the given fingerprint. So it returns the public keys one would use for plotting (it is the same farmer and pool pk as chia keys show)

Some alternative names:
get_plotting_public_keys
get_plotting_pks
get_farmer_pool_public_keys
get_farmer_pool_pks
get_pks_for_plotting
get_keys_for_plotting

[ChiaMineJP]

@emlowe I picked up get_keys_for_plotting.