Merge #10303: [bench] Include ms/blk stats in Connect* benchmarks.

Summary:
a473eff [bench] Replace 0.00(000)1 with MICRO/MILLI #defines in validation.cpp. (Karl-Johan Alm)
5f850b0 [bench] Include ms/blk stats in Connect* benchmarks. (Karl-Johan Alm)

Pull request description:

Display the average per block runtime for the various benchmarked times in the block connect functions to give an overview of long(er) term time distribution statistics.

Tree-SHA512: 3d6f24f6b9e3dbb448a647e2cda8e7b90ad6a16d4821f49f426a8e1ebc3ce5a0cf0a8cde82213e293affba441615702dfe50822c8c818e282af03bfe383d83e0

Backport of Core PR10303
Completes T520

Test Plan:

ninja
bitcoind

Verify debug.log output matches new format.

Reviewers: deadalnix, Fabien, #bitcoin_abc

Reviewed By: deadalnix, Fabien, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2320