feat: Trim `0x` prefix when creating `PrivateKey` from string

[0xivanov]

Description:

Related issue(s):

Fixes #1057

Notes for reviewer:

Checklist

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

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 73.82%. Comparing base (dabcc0b) to head (9e66330). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1059 +/- ## ======================================= Coverage 73.82% 73.82% ======================================= Files 174 174 Lines 24800 24801 +1 ======================================= + Hits 18309 18310 +1 Misses 5754 5754 Partials 737 737 ```

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