fix: h/m/l issues found with Slither

[fforbeck]

Proposed Changes

• Fixed all High/Medium/Low issues found with Slither, and disabled false positives.
• There are 3 issues related to the Offchain adapter that will be fixed in another PR (feat: voting rights #451) due to the breaking changes.
• Updated the slither gh workflow to check for high/med/low issues (it breaks the build if any issue is found).

[codecov]

Codecov Report

Merging #455 (7ce24f3) into master (37d1256) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #455   +/-   ##
=======================================
  Coverage   81.64%   81.64%           
=======================================
  Files          47       47           
  Lines        1743     1743           
  Branches      412      412           
=======================================
  Hits         1423     1423           
  Misses        320      320           

Impacted Files	Coverage Δ
contracts/adapters/Managing.sol	100.00% <ø> (ø)
...ntracts/adapters/voting/KickBadReporterAdapter.sol	0.00% <ø> (ø)
contracts/extensions/bank/BankFactory.sol	100.00% <ø> (ø)
...ensions/token/erc20/ERC20TokenExtensionFactory.sol	100.00% <ø> (ø)
contracts/adapters/CouponOnboarding.sol	88.88% <100.00%> (ø)
contracts/adapters/KycOnboarding.sol	93.05% <100.00%> (ø)

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