abci-cli: Add process_proposal command to abci-cli (#8901)

* Add `process_proposal` command to abci-cli

* Added process proposal to the 'tutorial' examples

* Added entry in CHANGELOG_PENDING.md

* Allow empty blocks in PrepareProposal, ProcessProposal, and FinalizeBlock

* Fix minimum arguments

* Add tests for empty block

* Updated abci-cli doc

Co-authored-by: Sergio Mena <sergio@informal.systems>
Co-authored-by: Jasmina Malicevic <jasmina.dustinac@gmail.com>

abci/tests/test_cli/ex1.abci

@@ -1,6 +1,7 @@
 echo hello
 info
 prepare_proposal "abc"
+process_proposal "abc"
 finalize_block "abc"
 commit
 info
@@ -8,4 +9,10 @@ query "abc"
 finalize_block "def=xyz" "ghi=123"
 commit
 query "def"
-prepare_proposal "preparedef"
+prepare_proposal "preparedef"
+process_proposal "def"
+process_proposal "preparedef"
+prepare_proposal
+process_proposal
+finalize_block
+commit

abci/tests/test_cli/ex1.abci.out

@@ -12,6 +12,10 @@
 -> code: OK
 -> log: Succeeded. Tx: abc action: UNMODIFIED
 
+> process_proposal "abc"
+-> code: OK
+-> status: ACCEPT
+
 > finalize_block "abc"
 -> code: OK
 -> code: OK
@@ -58,3 +62,24 @@
 -> code: OK
 -> log: Succeeded. Tx: preparedef action: REMOVED
 
+> process_proposal "def"
+-> code: OK
+-> status: ACCEPT
+
+> process_proposal "preparedef"
+-> code: OK
+-> status: REJECT
+
+> prepare_proposal 
+
+> process_proposal 
+-> code: OK
+-> status: ACCEPT
+
+> finalize_block 
+-> code: OK
+-> data.hex: 0x0600000000000000
+
+> commit 
+-> code: OK
+