propose pending_window of 2

[zancas]

This change shortens the wait time to remove a stale transaction (validator rejected) from 100 to 2.

It matches this request:

Fixes: #1563

[zancas]

I ran this test 10 times to check for intermittent effects.
Side effect, this test is now "fast" because is generates fewer blocks:

 Nextest run ID ca63541f-2d8c-4840-b651-05ef6b14383b with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  40.004s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  40.005s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.14s
------------
 Nextest run ID a034782d-4a00-427b-bb93-4e8195ffadc9 with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  39.606s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  39.607s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.14s
------------
 Nextest run ID 45832779-7e19-4f09-a4eb-55fdf4270f00 with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.617s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.618s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.14s
------------
 Nextest run ID 0115f6b6-646f-4c66-8c40-c1a1fcf04aa1 with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.614s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.615s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.14s
------------
 Nextest run ID 1eca71bc-2fc5-443c-8292-25d63c21bdb0 with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.626s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.627s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.13s
------------
 Nextest run ID eabfdb3d-a261-46a6-81f3-59cfb0bdbb5e with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.615s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.615s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.14s
------------
 Nextest run ID 659c52b1-3d7b-45cd-8be3-01de62d5bbd6 with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.617s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.617s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.13s
------------
 Nextest run ID 81df5e2a-9910-4e7c-a9cb-def59f1ef60f with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.622s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.622s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.13s
------------
 Nextest run ID b6e7a757-8cf3-412c-9991-63993742582a with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.641s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.641s] 1 test run: 1 passed, 367 skipped
    Finished `test` profile [optimized] target(s) in 0.14s
------------
 Nextest run ID 854a783f-a3ac-44ae-aa03-0a82304faf89 with nextest profile: default
    Starting 1 test across 18 binaries (367 tests skipped)
        PASS [  38.616s] libtonode-tests::concrete fast::mempool_clearing_and_full_batch_syncs_correct_trees
------------
     Summary [  38.617s] 1 test run: 1 passed, 367 skipped

[zancas]

Please wait for CLT pass before merging.

[zancas]

CLT passes, this is review ready.

[juanky201271]

I trust in you.