refactor: optimize field modifications in unsafe replacement

[derklaro]

Motivation

Currently the replacement methods for field access are implemented very inefficient, leading to performance problems when a lot of calls are being made to them.

Modification

1. Migrated away from passing around fields to wrapping them into a FieldAccessor instance which caches a VarHandle and optionally a MethodHandle instance for accessing/modifying the wrapped field.
2. Changed the FieldOffsetOps to cache these FieldAccessors instead of caching the Fields.
3. Changed the FieldOffsetOps to use a lock-free caching solution based on ClassValue and a FieldAccessor array, rather than using a ConcurrentHashMap with a custom key type.
4. Reduced the complexity when using the VarHandle/MethodHandle instance for a field by introducing a dummy Object argument for static fields to allow passing an instance when none is actually needed.

Result

The unsafe replacement methods for field access improved significantly leading to way better server performance under certain circumstances.

[github-actions]

Test Results

 56 files  ±0   56 suites  ±0   2m 40s ⏱️ +48s
570 tests ±0  570 ✅ ±0  0 💤 ±0  0 ❌ ±0 
935 runs  ±0  935 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 650a860. ± Comparison against base commit 6b4ee4d.

This pull request removes 34 and adds 34 tests. Note that renamed tests count towards both.

eu.cloudnetservice.driver.impl.document.DocumentSerialisationTest ‑ [4] {"b":1,"s":2,"i":3,"l":4,"f":5.0,"d":6.0,"c":"/","string":"Hello, World!","bol":true,"cloud":["Ben?","Yes","No","HoHoHoHo"],"world":{"this":"is","hello":"world","insane":"!"}}, PRETTY
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [14] 2025-08-24
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [23] 13:29:16.407343809
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [28] 13:29:16.407456850Z
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [29] 13:29:16.407477989Z
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [30] 13:29:16.407500441+05:00
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [31] 13:29:16.407517333-03:00
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [34] 2025-08-24T13:29:16.407648227
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [39] 2025-08-24T13:29:16.407805992Z
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [4] 2025-08-24T13:29:16.399239740Z
…

eu.cloudnetservice.driver.impl.document.DocumentSerialisationTest ‑ [4] {"b":1,"s":2,"i":3,"l":4,"f":5.0,"d":6.0,"c":"/","string":"Hello, World!","bol":true,"cloud":["Ben?","Yes","No","HoHoHoHo"],"world":{"insane":"!","this":"is","hello":"world"}}, PRETTY
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [14] 2025-09-03
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [23] 08:15:39.426503778
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [28] 08:15:39.426627972Z
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [29] 08:15:39.426651636Z
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [30] 08:15:39.426676283+05:00
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [31] 08:15:39.426697953-03:00
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [34] 2025-09-03T08:15:39.426834330
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [39] 2025-09-03T08:15:39.426991415Z
eu.cloudnetservice.driver.impl.document.gson.JavaTimeSerializerTest ‑ [4] 2025-09-03T08:15:39.415704288Z
…

♻️ This comment has been updated with latest results.