Add v7-to-v8 migration guide

[uglide]

Note

Low Risk
Documentation-only change; no runtime or library code is modified.

Overview
Adds a Jedis 7.5 → 8.0 migration guide (docs/migration-guides/v7-to-v8.md) and links it in MkDocs under Migrating to newer versions as Jedis 8.

The guide documents breaking changes (RESP3 auto-negotiation by default, TLS hostname verification, removal of JedisPooled/JedisSentineled and UnifiedJedis public constructors, Transaction/ClusterPipeline/CommandObjects/broadcastCommand API changes, deleted sharding utils, commons-pool2 2.13.1), deprecations (JedisCluster, legacy SSL setters, RediSearch cursor APIs), and v8 features (cluster request/response policies, RESP3 push handling, ftAggregateIterator, configGet/configSet, shared pipeline executor, sentinel pool map), with before/after Java snippets.

^{Reviewed by Cursor Bugbot for commit b3460a5. Bugbot is set up for automated code reviews on this repo. Configure here.}

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}

[github-actions]

Test Results

  203 files  ±0    203 suites  ±0   9m 53s ⏱️ +12s
7 767 tests ±0  7 705 ✅ +724  62 💤  - 724  0 ❌ ±0 
7 787 runs  ±0  7 725 ✅ +726  62 💤  - 726  0 ❌ ±0 

Results for commit 15498e8. ± Comparison against base commit 9a2dcd5.

♻️ This comment has been updated with latest results.

[uglide]

Compiled html is here https://github.com/redis/jedis/actions/runs/26389452267

[ggivo]

LGTM,
Some small findings

Should we also consider adding "TLS hostname verification is now enforced by default " - #4495