Close buffer accounts (bp #15887) (#15971)

* Add Close instrruction and tooling to upgradeable loader (#15887)

(cherry picked from commit 7f500d610c)

# Conflicts:
#	cli/src/program.rs
#	programs/bpf_loader/src/lib.rs

* resolve conflicts

* slice fill not supported on older rust

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

sdk/program/src/bpf_loader_upgradeable.rs

@@ -227,6 +227,20 @@ pub fn set_upgrade_authority(
     Instruction::new(id(), &UpgradeableLoaderInstruction::SetAuthority, metas)
 }
 
+/// Returns the instructions required to close an account
+pub fn close(
+    close_address: &Pubkey,
+    recipient_address: &Pubkey,
+    authority_address: &Pubkey,
+) -> Instruction {
+    let metas = vec![
+        AccountMeta::new(*close_address, false),
+        AccountMeta::new(*recipient_address, false),
+        AccountMeta::new_readonly(*authority_address, true),
+    ];
+    Instruction::new_with_bincode(id(), &UpgradeableLoaderInstruction::Close, metas)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

sdk/program/src/loader_upgradeable_instruction.rs

@@ -107,4 +107,13 @@ pub enum UpgradeableLoaderInstruction {
     ///   2. `[]` The new authority, optional, if omitted then the program will
     ///      not be upgradeable.
     SetAuthority,
+
+    /// Closes an account owned by the upgradeable loader of all lamports and
+    /// withdraws all the lamports
+    ///
+    /// # Account references
+    ///   0. `[writable]` The account to close.
+    ///   1. `[writable]` The account to deposit the closed account's lamports.
+    ///   2. `[signer]` The account's authority.
+    Close,
 }