docs: Add notes on how to diasble rpc timeout in functional tests while attatching gdb.

Author: rajarshimaitra

test/README.md

@@ -225,6 +225,10 @@ gdb /home/example/bitcoind <pid>
 Note: gdb attach step may require ptrace_scope to be modified, or `sudo` preceding the `gdb`.
 See this link for considerations: https://www.kernel.org/doc/Documentation/security/Yama.txt
 
+Often while debugging rpc calls from functional tests, the test might reach timeout before
+process can return a response. Use `--timeout-factor 0` to disable all rpc timeouts for that partcular
+functional test. Ex: `test/functional/wallet_hd.py --timeout-factor 0`.
+
 ##### Profiling
 
 An easy way to profile node performance during functional tests is provided