Allow closing upgradeable program accounts (backport #19319) (#19411)

* Allow closing upgradeable program accounts (#19319)

(cherry picked from commit a89f180145)

# Conflicts:
#	programs/bpf_loader/src/lib.rs
#	programs/bpf_loader/src/syscalls.rs
#	sdk/src/feature_set.rs

* resolve conflicts

Co-authored-by: Jack May <jack@solana.com>
Co-authored-by: Justin Starry <justin@solana.com>

sdk/program/src/loader_upgradeable_instruction.rs

@@ -112,8 +112,12 @@ pub enum UpgradeableLoaderInstruction {
     /// withdraws all the lamports
     ///
     /// # Account references
-    ///   0. `[writable]` The account to close.
+    ///   0. `[writable]` The account to close, if closing a program must be the
+    ///      ProgramData account.
     ///   1. `[writable]` The account to deposit the closed account's lamports.
-    ///   2. `[signer]` The account's authority.
+    ///   2. `[signer]` The account's authority, Optional, required for
+    ///      initialized accounts.
+    ///   3. `[writable]` The associated Program account if the account to close
+    ///      is a ProgramData account.
     Close,
 }