Reimplement `backtrace-on-redisplay-error` using `push_handler_bind`.
This moves the code from `signal_or_quit` to `xdisp.c` and
`debug-early.el`.

* lisp/emacs-lisp/debug-early.el (debug-early-backtrace):
Add `base` arg to strip "internal" frames.
(debug--early): New function, extracted from `debug-early`.
(debug-early, debug-early--handler): Use it.
(debug-early--muted): New function, extracted (translated) from
`signal_or_quit`; trim the buffer to a max of 10 backtraces.

* src/xdisp.c (funcall_with_backtraces): New function.
(dsafe_calln): Use it.
(syms_of_xdisp): Defsym `Qdebug_early__muted`.

* src/eval.c (redisplay_deep_handler): Delete var.
(init_eval, internal_condition_case_n): Don't set it any more.
(backtrace_yet): Delete var.
(signal_or_quit): Remove special case for `backtrace_on_redisplay_error`.
* src/keyboard.c (command_loop_1): Don't set `backtrace_yet` any more.
* src/lisp.h (backtrace_yet): Don't declare.

`macroexp--with-extended-form-stack` used manual push/pop so that upon
non-local exits the "deeper" value is kept, so the error handler gets
to know what was the deeper value, so as to be able to compute more
precise error locations.
Replace this with a `handler-bind` which catches that "deeper" value
more explicitly.

* lisp/emacs-lisp/bytecomp.el (bytecomp--displaying-warnings):
Use `handler-bind` to catch the value of `byte-compile-form-stack`
at the time of the error.  Also consolidate the duplicated code.

* lisp/emacs-lisp/macroexp.el (macroexp--with-extended-form-stack):
Use a plain dynbound let-rebinding.

Move ad-hoc code meant to ease debugging of bootstrap (and batch mode)
to `top_level_2` so it doesn't pollute `signal_or_quit`.

* src/lisp.h (pop_handler, push_handler_bind): Declare.
* src/keyboard.c (top_level_2): Setup an error handler to call
`debug-early` when noninteractive.
* src/eval.c (pop_handler): Not static any more.
(signal_or_quit): Remove special case for noninteractive use.
(push_handler_bind): New function, extracted from `Fhandler_bind_1`.
(Fhandler_bind_1): Use it.
(syms_of_eval): Declare `Qdebug_early__handler`.
* lisp/emacs-lisp/debug-early.el (debug-early-backtrace): Weed out
frames below `debug-early`.
(debug-early--handler): New function.

This provides a more reliable fix for bug#65267 since we don't
touch `debug-on-error` nor `debug-ignore-errors` any more.

* lisp/startup.el (startup--debug): New function.
(startup--load-user-init-file): Use it and `handler-bind` instead of
let-binding `debug-on-error`.

* lisp/emacs-lisp/ert.el (ert--should-signal-hook): Delete function.
(ert--expand-should-1): Don't bind `signal-hook-function`.
(ert--test-execution-info): Remove `next-debugger` slot.
(ert--run-test-debugger): Adjust to new calling convention.
Pass the `:backtrace-base` info to the debugger.
(ert--run-test-internal): Use `handler-bind` rather than let-binding
`debugger` and `debug-on-error`.

* lisp/emacs-lisp/ert-x.el (ert-remote-temporary-file-directory): Don't
use `defconst` if it's not meant to stay constant (e.g. we let-bind it
in tramp-tests.el).

* lisp/simple.el (eval-expression--debug): New function.
(eval-expression): Use it together with `handler-bind` instead of
let-binding `debug-on-error`.

AFAIK, this provides the same semantics as Common Lisp's `handler-bind`,
modulo the differences about how error objects and conditions are
represented.

* lisp/subr.el (handler-bind): New macro.

* src/eval.c (pop_handler): New function.
(Fhandler_Bind_1): New function.
(signal_or_quit): Handle new handlertypes `HANDLER` and `SKIP_CONDITIONS`.
(find_handler_clause): Simplify.
(syms_of_eval): Defsubr `Fhandler_bind_1`.

* doc/lispref/control.texi (Handling Errors): Add `handler-bind`.

* test/src/eval-tests.el (eval-tests--handler-bind): New test.

* lisp/emacs-lisp/lisp-mode.el (lisp-font-lock-keywords):
Move 'handler-bind' from CL-only to generic Lisp.
(handler-bind): Remove indentation setting, it now lives in the macro
definition.

* lisp/vc/vc-hooks.el (vc-use-short-revision): New variable.
(vc-short-revision): New function.

* lisp/vc/vc-annotate.el (vc-annotate-use-short-revision): New
option...
(vc-annotate): ... use it.

* lisp/vc/vc-git.el (vc-git--rev-parse): Consult
'vc-use-short-revision'.

* etc/NEWS: Announce this change (bug#67062).

* lisp/progmodes/eglot.el
(eglot-alternatives)
(eglot-server-programs): : Rework docstring.
(eglot--guess-contact): Pass project to eglot-server-programs function.
(project-root): Define for new experimental Eglot project type.

Github-reference: https://github.com/joaotavora/eglot/discussions/1337