This file was originally generated by dumping symbols from a running JDK, so it contains many symbols from the JDK:

http://hg.openjdk.java.net/jdk/jdk/file/94fe833a244b/test/hotspot/jtreg/runtime/cds/appcds/ExtraSymbols.symbols.txt

This has caused confusions when developers are removing APIs from the JDK, and they are not sure if they should also remove the corresponding symbols in this file.

(FYI, developers should simply leave this file alone when removing APIs from the JDK).

There's no need to use actual JDK symbols in this file. So let's remove it and replace with logic in the test to auto-generate a file with a lot of symbols.