Remove saving grace

This feature was no longer fulfilling its intended purpose: the
issue is that when players are aware of it, instead of creating
interesting stories, it becomes a resource the player can rely on.

Alternative mitigation for some "unfair" early-game deaths has been
added (such as the warning shot for early-game attack wands and the
ability of iron shoes to protect against certain early traps), and
the warning shot in particular can create interesting gameplay
moments and stories of its own, especially when saving grace is
*not* present (discovering that a monster has a wand of fire and
can oneshot you is an interesting emergency situation, but less
scary if you know that its first attempt to oneshot you will fail).

The feature was also proving quite hard to code correctly, because
there are numerous cases that it "obviously" shouldn't affect
(most notably beheading due to Vorpal Blade, but also things like
purple worm digestion) which would need to be special-cased, and
because there are grey areas like wand zap bounces (which might or
might not be an intentional attempt by the player to hit themself
with the bounce) and damage from traps. Removing it saves the need
to work out, for every new damage source, whether and when saving
grace should interact with it.

Breaks save compatibility.

doc/fixes3-7-0.txt

@@ -2219,9 +2219,6 @@ uncursed genocide while hallucinating deliberately mis-reports hero's role as
 	target but was also inappropriately showing it to livelog/#chronicle
 livelog/#chronicle for bribing a demon lord reported random monster and
 	currency if hero was hallucinating
-livelog/#chronicle for saving-grace: if saving-grace prevents hero's death,
-	report it [at present, it uses the livelog classification for breaking
-	a conduct]
 naming a type of item, unnaming it (with name of <space>), naming it again
 	(new name or re-use of old one), then unnaming it again would issue
 	impossible: "named object not in disco"
@@ -2904,11 +2901,6 @@ pyrolisk eggs explode when broken
 pauper-option to start the character with no possessions
 wand of secret door detection, spell of detect unseen, and wizard mode ^E now
 	flash the cursor at each location where detection finds something
-saving-grace: once per game if receiving a killing blow from full or nearly
-	full HP, survive with 1 HP
-enlightenment/attribute disclosure for saving-grace: include a line for have
-	or haven't been saved (game in progress) or did or didn't get saved
-	(game over) via saving-grace
 'selectsaved' lists "name-role-race-gend-algn" instead of just "name" in the
 	menu of save files available to be restored
 'selectsaved' prefixes "name-role-race-gend-algn" with "- " for normal play,