cmd/compile: enable scopes unconditionally

This revives Alessandro Arzilli's CL to enable scopes
whenever any dwarf is emitted (with optimization or not),
adds a test that detects this changes and shows that it
creates more truthful debugging output.

Reverted change to ssa/debug_test tests made when
scopes were disabled during dwarflocationlist development.

Also included are updates to the Delve test output (it
had fallen out of sync; creating test output for one
updates it for all) and minor naming changes in
ssa/debug_test.

Compile-time/space changes (relative to tip including dwarflocationlists):

benchstat -geomean after.log scopes.log
name        old time/op     new time/op     delta
Template        182ms ± 1%      182ms ± 1%    ~     (p=0.666 n=9+9)
Unicode        82.8ms ± 1%     86.6ms ±14%    ~     (p=0.211 n=9+10)
GoTypes         611ms ± 1%      616ms ± 2%  +0.97%  (p=0.001 n=10+9)
Compiler        2.95s ± 1%      2.95s ± 0%    ~     (p=0.573 n=10+8)
SSA             6.70s ± 1%      6.81s ± 1%  +1.68%  (p=0.000 n=9+10)
Flate           117ms ± 1%      118ms ± 1%  +0.60%  (p=0.036 n=9+8)
GoParser        145ms ± 1%      145ms ± 1%    ~     (p=1.000 n=9+9)
Reflect         398ms ± 1%      396ms ± 1%    ~     (p=0.053 n=9+10)
Tar             171ms ± 1%      171ms ± 1%    ~     (p=0.356 n=9+10)
XML             214ms ± 1%      214ms ± 1%    ~     (p=0.605 n=9+9)
StdCmd          12.4s ± 2%      12.4s ± 1%    ~     (p=1.000 n=9+9)
[Geo mean]      506ms           509ms       +0.71%

name        old user-ns/op  new user-ns/op  delta
Template         254M ± 4%       249M ± 6%    ~     (p=0.155 n=10+10)
Unicode          121M ±11%       124M ± 6%    ~     (p=0.516 n=10+10)
GoTypes          824M ± 2%       869M ± 5%  +5.49%  (p=0.001 n=8+10)
Compiler        4.01G ± 2%      4.02G ± 1%    ~     (p=0.561 n=9+9)
SSA             10.0G ± 2%      10.2G ± 2%  +2.29%  (p=0.000 n=9+10)
Flate            154M ± 7%       154M ± 7%    ~     (p=0.960 n=10+9)
GoParser         190M ± 7%       196M ± 6%    ~     (p=0.064 n=9+10)
Reflect          528M ± 2%       517M ± 3%  -1.97%  (p=0.025 n=10+10)
Tar              227M ± 5%       232M ± 3%    ~     (p=0.061 n=9+10)
XML              286M ± 4%       283M ± 4%    ~     (p=0.343 n=9+9)
[Geo mean]       502M            508M       +1.09%

name        old text-bytes  new text-bytes  delta
HelloSize        672k ± 0%       672k ± 0%  +0.01%  (p=0.000 n=10+10)
CmdGoSize       7.21M ± 0%      7.21M ± 0%  -0.00%  (p=0.000 n=10+10)
[Geo mean]      2.20M           2.20M       +0.00%

name        old data-bytes  new data-bytes  delta
HelloSize       9.88k ± 0%      9.88k ± 0%    ~     (all equal)
CmdGoSize        248k ± 0%       248k ± 0%    ~     (all equal)
[Geo mean]      49.5k           49.5k       +0.00%

name        old bss-bytes   new bss-bytes   delta
HelloSize        125k ± 0%       125k ± 0%    ~     (all equal)
CmdGoSize        144k ± 0%       144k ± 0%  -0.04%  (p=0.000 n=10+10)
[Geo mean]       135k            135k       -0.02%

name        old exe-bytes   new exe-bytes   delta
HelloSize       1.30M ± 0%      1.34M ± 0%  +3.15%  (p=0.000 n=10+10)
CmdGoSize       13.5M ± 0%      13.9M ± 0%  +2.70%  (p=0.000 n=10+10)
[Geo mean]      4.19M           4.31M       +2.92%

Change-Id: Id53b8d57bd00440142ccbd39b95710e14e083fb5
Reviewed-on: https://go-review.googlesource.com/101217
Reviewed-by: Heschi Kreinick <heschi@google.com>

src/cmd/compile/internal/gc/main.go

@@ -405,7 +405,7 @@ func Main(archInit func(*Arch)) {
 		Debug['l'] = 1 - Debug['l']
 	}
 
-	trackScopes = flagDWARF && (Debug['l'] == 0 && Debug['N'] != 0)
+	trackScopes = flagDWARF
 
 	Widthptr = thearch.LinkArch.PtrSize
 	Widthreg = thearch.LinkArch.RegSize