This reverts commit 0519a75f6eca1065a4d0184f99c71ae03a99b9b1.

Problem:    Peeking and flushing output slows down execution.
Solution:   Do not update the mode message when global_busy is set.  Do not
            flush when only peeking for a character. (Ken Takata)
https://github.com/vim/vim/commit/cb574f415486adff645ce384979bfecf27f5be8c

The following keeps happening in my local environment
because the timeout is too short.

[  FAILED  ] test/functional/eval/timer_spec.lua @ 208: timers do not crash when processing events in the handler
test/functional/eval/timer_spec.lua:219: retry() attempts: 1
test/helpers.lua:73: Expected objects to be the same.
Passed in:
(number) 0
Expected:
(number) 1

Those are flaky when using luacov (which causes reproducible slowness).

E.g.:

    [  ERROR   ] test/functional\eval\timer_spec.lua @ 105: timers can invoke redraw in blocking getchar() call
    test\functional\ui\screen.lua:587: Row 3 did not match.
    Expected:
      |ITEM 1                                  |
      |ITEM 2                                  |
      |*{1:~                                       }|
      |{1:~                                       }|
      |{1:~                                       }|
      |^                                        |
    Actual:
      |ITEM 1                                  |
      |ITEM 2                                  |
      |*ITEM 3                                  |
      |{1:~                                       }|
      |{1:~                                       }|
      |^                                        |

ref #10768

It was increased in dd21cd2a4 to avoid flakiness, but takes 1s then always.

This specifies a shorter timeout again, uisng `load_adjust`.

Ref: https://github.com/neovim/neovim/pull/10768#discussion_r315904175

Co-Authored-By: Justin M. Keyes <justinkz@gmail.com>

Inspired by quickbuild failure, where `g:val` was increased already:

    20:07:04,227 INFO  - not ok 1164 - timers works with repeat two
    20:07:04,227 INFO  - # test/functional/eval/timer_spec.lua @ 36
    20:07:04,227 INFO  - # Failure message: test/functional/eval/timer_spec.lua:38: Expected objects to be the same.
    20:07:04,227 INFO  - # Passed in:
    20:07:04,227 INFO  - # (number) 1
    20:07:04,227 INFO  - # Expected:
    20:07:04,227 INFO  - # (number) 0
    20:07:04,227 INFO  - # stack traceback:
    20:07:04,227 INFO  - #     test/functional/eval/timer_spec.lua:38: in function <test/functional/eval/timer_spec.lua:36>

Uses a pattern of `eq()`ing `timer_start` and `g:val` in the same `eval`
call, and decreases timeouts in general.

Improves runtime from ~5s to <2s.

Seen on quickbuild:

    23:01:01,289 INFO  - not ok 1172 - timers can be stopped from the handler
    23:01:01,289 INFO  - # test/functional/eval/timer_spec.lua @ 154
    23:01:01,289 INFO  - # Failure message: test/functional/eval/timer_spec.lua:166: Expected objects to be the same.
    23:01:01,289 INFO  - # Passed in:
    23:01:01,289 INFO  - # (number) 3
    23:01:01,289 INFO  - # Expected:
    23:01:01,289 INFO  - # (number) 0
    23:01:01,289 INFO  - # stack traceback:
    23:01:01,289 INFO  - # 	test/functional/eval/timer_spec.lua:166: in function <test/functional/eval/timer_spec.lua:154>

Log: http://neovim-qb.szakmeister.net/build/24288
Ref: https://github.com/neovim/neovim/pull/10364