test: introduce tests in common module

[ata-nas]

Description:

• add tests in the :common module

Related issue(s):
Fixes #273

Notes for reviewer:

• am I missing some tests or edge cases?

Checklist

• add unit tests for com.hedera.block.common.utils.StringUtilities
• add unit tests for com.hedera.block.common.utils.FileUtilities

---

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[AlfredoG87]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.59%. Comparing base (560404c) to head (af0e133).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #274      +/-   ##
============================================
- Coverage     99.78%   99.59%   -0.20%     
- Complexity      259      272      +13     
============================================
  Files            52       54       +2     
  Lines           938      981      +43     
  Branches         64       70       +6     
============================================
+ Hits            936      977      +41     
- Misses            2        3       +1     
- Partials          0        1       +1     

see 2 files with indirect coverage changes