Metrics (Block processing lock): Number of times + duration

[freemanzMrojo]

Description

Metrics taken based on the description for Block processing lock here https://github.com/vechain/protocol-board-repo/issues/340 and taking metricBlockProcessedCount and metricBlockProcessedDuration as a reference.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 61.53%. Comparing base (571f607) to head (9b3076c).

Files with missing lines	Patch %	Lines
cmd/thor/node/node.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           feat/db     #934      +/-   ##
===========================================
- Coverage    61.54%   61.53%   -0.01%     
===========================================
  Files          217      217              
  Lines        22635    22641       +6     
===========================================
+ Hits         13930    13933       +3     
- Misses        7583     7587       +4     
+ Partials      1122     1121       -1     

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[libotony]

As block processing duration is already captured, I would suggest this metric to be redundant.