feat: adds cache: prefix to all CacheService keys

[simzzz]

Description

CacheService stores Redis keys without a prefix, while other services use prefixes (pending:*, hbar-limit:*, etc.). This causes:

1. Unsafe clearing: CacheService.clear() can't distinguish its keys from others, so we hardcode a filter:

   const keysToDelete = allKeys.filter((key) => !key.startsWith('pending:'));

   This couples RedisCache to TransactionPoolService and doesn't scale.

2. No ownership: Can't tell which keys belong to which service.

3. Maintenance burden: Every new Redis user must update the filter.

This PR solves that by adding the prefix to all CacheService keys. The pending: key was also changed to txpool:pending. All tests have been added to reflect that.

Related issue(s)

Fixes #4501

Testing Guide

1. Call any method using cache
2. Check keys in Redis

Changes from original design (optional)

N/A

Additional work needed (optional)

N/A

Checklist

• I've assigned an assignee to this PR and related issue(s) (if applicable)
• I've assigned a label to this PR and related issue(s) (if applicable)
• I've assigned a milestone to this PR and related issue(s) (if applicable)
• I've updated documentation (code comments, README, etc. if applicable)
• I've done sufficient testing (unit, integration, etc.)

[github-actions]

Test Results

 20 files  ±0  269 suites  ±0   21m 51s ⏱️ -19s
778 tests ±0  774 ✅ +1  4 💤 ±0  0 ❌  - 1 
794 runs  ±0  790 ✅ +1  4 💤 ±0  0 ❌  - 1 

Results for commit c201a06. ± Comparison against base commit 65c2bb1.

♻️ This comment has been updated with latest results.

[quiet-node]

LGTM

[codecov]

Codecov Report

❌ Patch coverage is 98.75000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
packages/relay/src/lib/clients/cache/redisCache.ts	97.82%	1 Missing ⚠️

@@            Coverage Diff             @@
##             main    #4559      +/-   ##
==========================================
+ Coverage   95.01%   95.53%   +0.51%     
==========================================
  Files         127      127              
  Lines       20447    20496      +49     
  Branches     1734     1759      +25     
==========================================
+ Hits        19427    19580     +153     
+ Misses       1000      897     -103     
+ Partials       20       19       -1     

Flag	Coverage Δ
config-service	98.81% <ø> (ø)
relay	90.95% <98.75%> (+0.02%)	⬆️
server	88.85% <ø> (ø)
ws-server	98.04% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...kages/relay/src/lib/clients/cache/localLRUCache.ts	93.70% <100.00%> (+0.47%)	⬆️
...ctionPoolService/RedisPendingTransactionStorage.ts	100.00% <100.00%> (ø)
packages/relay/src/lib/clients/cache/redisCache.ts	94.13% <97.82%> (+0.60%)	⬆️

... and 5 files with indirect coverage changes

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