chore: override toString methods in records

[Grigorov-Georgi]

Description:

Override the default toString() in SchnorrKeyPair and TssKeyPair records to output only its public key.

Notes for reviewer:

Checklist

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

[lfdt-bot]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@             Coverage Diff              @@
##               main   #26817      +/-   ##
============================================
- Coverage     70.44%   70.44%   -0.01%     
+ Complexity    11673    11672       -1     
============================================
  Files          2583     2583              
  Lines        108354   108357       +3     
  Branches      12122    12122              
============================================
+ Hits          76332    76333       +1     
+ Misses        28035    28034       -1     
- Partials       3987     3990       +3     

Files with missing lines	Coverage Δ	Complexity Δ
...a/node/app/history/impl/ProofKeysAccessorImpl.java	95.12% <100.00%> (+0.12%)	0.00 <0.00> (ø)
...main/java/com/hedera/node/app/tss/TssKeyFiles.java	76.99% <100.00%> (+0.20%)	0.00 <0.00> (ø)
.../main/java/com/hedera/node/app/tss/TssKeyPair.java	100.00% <100.00%> (ø)	0.00 <0.00> (ø)

... and 8 files with indirect coverage changes

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[testlens-app]

✅ All tests passed ✅

🏷️ Commit: da73b29
▶️ Tests: 52182 executed
🟡 Checks: 56/69 completed

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