Drop write lock on sysvars (#15497)

* Drop write lock on sysvars

* adds env var for demoting sysvar write lock demotion

* moves demote logic to is_writable

* feature gates sysvar write lock demotion

* adds builtins to write lock demotion

* adds system program id to builtins

* adds Feature111...

* adds an abi-freeze test

* mvines set of builtin program keys

Co-authored-by: Michael Vines <mvines@gmail.com>

* update tests

* adds bpf loader keys

* Add test sysvar

* Plumb demote_sysvar to is_writable

* more plumbing of demote_sysvar_write_locks to is_writable

* patches test_program_bpf_instruction_introspection

* hard codes demote_sysvar_write_locks to false for serialization/encoding methods

* Revert "hard codes demote_sysvar_write_locks to false for serialization/encoding methods"

This reverts commit ae3e2d2e777437bddd753933097a210dcbc1b1fc.

* change the hardcoded ones to demote_sysvar_write_locks=true

* Use data_as_mut_slice

Co-authored-by: behzad nouri <behzadnouri@gmail.com>
Co-authored-by: Michael Vines <mvines@gmail.com>

programs/bpf/tests/programs.rs

@@ -1323,7 +1323,9 @@ fn test_program_bpf_instruction_introspection() {
     let result = bank_client.send_and_confirm_instruction(&mint_keypair, instruction);
     assert_eq!(
         result.unwrap_err().unwrap(),
-        TransactionError::InvalidAccountIndex
+        // sysvar write locks are demoted to read only. So this will no longer
+        // cause InvalidAccountIndex error.
+        TransactionError::InstructionError(0, InstructionError::ProgramFailedToComplete),
     );
 
     // No accounts, should error