tests: fix dependency on global counters

[algonautshant]

These tests depend on global counters. Depending on the order of the tests running, they might interfere with each other, or interfere with parallel running tests.

This change forces such tests not to run in parallel, and initializes and resets the global counters.

In addition, cleanup of resources (ledger close, exec pool shutdown) which are not returned when the tests finish and consume memory and threads unnecessarily.

[codecov]

Codecov Report

Merging #4921 (cf43e3e) into master (89ed675) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4921      +/-   ##
==========================================
- Coverage   53.55%   53.53%   -0.02%     
==========================================
  Files         431      431              
  Lines       53533    53533              
==========================================
- Hits        28667    28660       -7     
- Misses      22643    22648       +5     
- Partials     2223     2225       +2     

Impacted Files	Coverage Δ
ledger/blockqueue.go	85.63% <0.00%> (-2.88%)	⬇️
agreement/cryptoVerifier.go	67.60% <0.00%> (-2.12%)	⬇️
agreement/proposalManager.go	96.07% <0.00%> (-1.97%)	⬇️
catchup/peerSelector.go	98.95% <0.00%> (-1.05%)	⬇️
data/transactions/verify/txn.go	73.72% <0.00%> (-0.85%)	⬇️
ledger/testing/randomAccounts.go	56.61% <0.00%> (-0.62%)	⬇️
catchup/service.go	70.53% <0.00%> (ø)
network/wsNetwork.go	64.74% <0.00%> (ø)
ledger/tracker.go	75.10% <0.00%> (+0.84%)	⬆️
crypto/merkletrie/node.go	93.48% <0.00%> (+1.86%)	⬆️
... and 1 more

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more