runtime(termdebug): improve the breakpoint sign label (vim/vim#13525)

// related vim/vim#12589
// that should be the last chat (I) with Bram, r.i.p

https://github.com/vim/vim/commit/2dd613f57bf17eb8ff050bcb5510eb0279f5c9ab

Co-authored-by: Shane-XB-Qian <shane.qian@foxmail.com>

Problem:    It is not easy to restore saved mappings.
Solution:   Make mapset() accept a dict argument. (Ernie Rael, closes vim/vim#10295)

https://github.com/vim/vim/commit/51d04d16f21e19d6eded98f9530d84089102f925

Co-authored-by: Ernie Rael <errael@raelity.com>

runtime(termdebug):  handle buffer-local mappings properly

closes: vim/vim#13475

https://github.com/vim/vim/commit/7fbbd7fdc6df9dc198b3735cfbe8dbe8afd646f9

Co-authored-by: shane.xb.qian <shane.qian@foxmail.com>

runtime(termdebug): improve window handling, shorten var types

closes vim/vim#13474

https://github.com/vim/vim/commit/ca48202b6f46cfb40a0d1d80033a2f3e8cb7b813

Co-authored-by: shane.xb.qian <shane.qian@foxmail.com>

Co-authored-by: Peter Aronoff <peter@aronoff.org>

runtime: Fix more typos (vim/vim#13354)

* Fix more typos

* Fix typos in ignored runtime/ directory

https://github.com/vim/vim/commit/dbf749bd5aaef6ea2d28bce081349785d174d96a

Co-authored-by: Viktor Szépe <viktor@szepe.net>

Mostly to make it more consistent and to match Vim more where applicable.

runtime(termdebug): more termdebug fixes and improvements (vim/vim#12892)

- Fix and attempt to simplify :Frame/:Up/:Down documentation.

- Accept a count instead for :Up/:Down/+/-.

- Update the "Last Change" dates.

- Fix a missing :let (caused an error if gdb fails to start).

- Wipe the prompt buffer when ending prompt mode (if it exists and wasn't wiped
  by the user first). Avoids issues with stale prompt buffers (such as E95 when
  starting a new prompt mode session).

- Kill the gdb job if the prompt buffer is unloaded (similar to what's done for
  a terminal buffer). Fixes not being able to start a new termdebug session if
  the buffer was wiped by the user, for example.

https://github.com/vim/vim/commit/3d3a9152fa6de7038fdfd6d6de25230ed825552a

runtime(termdebug): add frame related commands (vim/vim#12511)

implementing `:Frame`, `:Up` and `:Down'

https://github.com/vim/vim/commit/2ae7ffe0bc3c3ed9fcae35ef23a2b78908580201

Use maparg() for saving K as it's since been ported (and supports Lua callbacks
and the other API fields).

Use the 3 argument variant of mapset(), as the single argument one isn't ported
yet (v8.2.4861).

Co-authored-by: Simon Sobisch <simonsobisch@web.de>

Unlike Vim's job_stop(), Nvim's jobstop() does not take a signal argument, and
always sends SIGTERM/KILL.

:Stop and Ctrl-C in prompt mode is supposed to interrupt the program like in
terminal mode, not kill GDB.

Also, maybe libuv's kill() works on Windows? If so, the logic above could be
removed, but I don't have a Windows machine available to test that.

Also "set nomodified" when ending prompt mode, like Vim (avoids E37).