Add a summary document about the ghc work/branches

Author: harendra-kumar

dev/ghc-work.md

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+## **GHC 8.8.4**
+
+### **Original Work**
+
+* **Tag:** `ghc-8.8.4-eventlog-enhancements`
+
+  * Introduced `threadCPUTime#` primop early in development.
+  * CPU time was initially measured using `clock_gettime` before and after thread execution in the scheduler.
+  * Later transitioned to **eventlog-based measurement**, making the primop unused in practice.
+
+#### ↳ **Follow-up Work**
+
+* **Tag:** `ghc-8.8.4-threadCPUTime-add-alloc-sched-count`
+
+  * Revived `threadCPUTime#` primop hooks.
+  * Added additional counters:
+
+    * Scheduler count
+    * Allocation tracking
+  * Enabled **in-memory performance data collection**, allowing:
+
+    * CPU time
+    * Allocations
+    * Scheduler count
+  * Works **without requiring eventlogs**.
+
+---
+
+## **GHC 8.10.7**
+
+### **Eventlog Enhancements Port**
+
+* **Tag:** `ghc-8.10.7-eventlog-enhancements`
+
+  * Port of eventlog-based counter work from 8.8.4.
+
+#### ↳ **Primop Enhancements**
+
+* **Tag:** `ghc-8.10.7-primop-enhancements`
+
+  * Port of in-memory performance counter collection using primops.
+
+##### ↳ **Debug Enhancements**
+
+* **Tag:** `ghc-8.10.7-debug-enhancements`
+
+  * Added tracing hooks in `forkOn`.
+  * Purpose:
+
+    * Track and account for all threads created
+    * Covers both:
+
+      * GHC runtime-created threads
+      * User-created threads
+
+---
+
+## **GHC 9.2.8**
+
+### **File Lock Debugging**
+
+* **Tag:** `ghc-9.2.8-file-lock-debug`
+
+  * Introduced debugging code for a file locking bug in GHC.
+
+### **Performance Counters (threadCPUTime#)**
+
+* **Tag:** `ghc-9.2.8-perf-counters-1-rc1`
+
+  * Port of the 8.10.7 `primop-enhancements` work.
+
+#### ↳ **Memory Leak Profiling**
+
+* **Tag:** `ghc-9.2.8-leak-profiling-1-rc1`
+
+  * Added work related to memory leak profiling.