The new oldtest directory is in test/old/testdir. The reason for this is
that many tests have hardcoded the parent directory name to be
'testdir'.

Problem:    Some tests fail when run under valgrind.
Solution:   Increase timeouts.

https://github.com/vim/vim/commit/353c351bd22e4dac4c3ae9cd7731032348f248c4

Cherry-pick Test_pum_with_preview_win() from patch 8.2.0011.

Co-authored-by: Bram Moolenaar <Bram@vim.org>

Problem:    Debugger code insufficiently tested.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes vim/vim#6700)

https://github.com/vim/vim/commit/16c6232cad40af37f37dc9c561392b7761b9e229

Problem:    Some tests fail when run under valgrind.
Solution:   Avoid timing problems.
https://github.com/vim/vim/commit/18dc355395f2eac72ab83d984cacd26ae61c791f

Co-authored-by: Elias Alves Moura <eliamoura.alves@gmail.com>
Co-authored-by: venkatesh <shariharanvenkatesh@gmail.com>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
Co-authored-by: Vikas Raj <24727447+numToStr@users.noreply.github.com>
Co-authored-by: Steve Vermeulen <sfvermeulen@gmail.com>
Co-authored-by: Evgeni Chasnovski <evgeni.chasnovski@gmail.com>
Co-authored-by: rwxd <rwxd@pm.me>
Co-authored-by: casswedson <58050969+casswedson@users.noreply.github.com>

Problem:    A failing debug expression may make Vim unusable.
Solution:   Suppress error messages. (closes vim/vim#8848)
https://github.com/vim/vim/commit/0325d3967ce7d0fd35bc1472fd476b911b895b76

Problem:    Vim9: a failing debug expression aborts script sourcing.
Solution:   Do not let expression failure abort script sourcing. (closes vim/vim#8848)
https://github.com/vim/vim/commit/072f1c68884a1e2d468a0f39e27fc28168fb4b03

Vim9script is N/A, exclude Test_Debugger_breakadd_expr.

Move debuggy struct to before generated header inclusion so
eval_expr_restore prototype works.

Add CheckRunVimInTerminal to Test_Debugger_breakadd.
Cherry-pick Test_Debugger_breakadd changes from v8.2.1440, v8.2.1736.

Problem:    Vim9: debugger test fails.
Solution:   Use "var" instead of "let".
https://github.com/vim/vim/commit/1bdae4032359081325578cc74739a0a097e008ff

Problem:    Not all debugger commands covered by tests.
Solution:   Add tests for going up/down in the stack. (Ben Jackson,
            closes vim/vim#6765)
https://github.com/vim/vim/commit/c63b72b6dc1347530ce906b462bb568994552c8b

Problem:    Insufficient testing for script debugging.
Solution:   Add more tests. (Ben Jackson)
https://github.com/vim/vim/commit/b7f4fa517793b0fe1a4895781b4cba451d60d7c2

Check terminal feature in individual tests, not the test suite.
Avoid code coverage loss in test_debugger.vim.