lang: core: Move template to golang namespace

I don't think this template function should be in any way authoritative,
so let's namespace it.

lang/interpret_test/TestAstFunc2/map-iterator0.txtar

@@ -1,4 +1,5 @@
 -- main.mcl --
+import "golang"
 import "iter"
 
 $fn = func($x) { # notable because concrete type is fn(t1) t2, where t1 != t2
@@ -9,7 +10,7 @@ $ins = ["a", "bb", "ccc", "dddd", "eeeee",]
 
 $out = iter.map($ins, $fn)
 
-$t = template("out: {{ . }}", $out)
+$t = golang.template("out: {{ . }}", $out)
 
 test "${t}" {}
 -- OUTPUT --

lang/interpret_test/TestAstFunc2/map-iterator1.txtar

@@ -1,4 +1,5 @@
 -- main.mcl --
+import "golang"
 import "iter"
 
 func itermap($a, $b) {
@@ -29,14 +30,14 @@ $out6 = iter.map($in4, func($x) { $x + $x })
 $out7 = itermap($in3, func($x) { $x + $x })
 $out8 = itermap($in4, func($x) { $x + $x })
 
-$t1 = template("out1: {{ . }}", $out1)
-$t2 = template("out2: {{ . }}", $out2)
-$t3 = template("out3: {{ . }}", $out3)
-$t4 = template("out4: {{ . }}", $out4)
-$t5 = template("out5: {{ . }}", $out5)
-$t6 = template("out6: {{ . }}", $out6)
-$t7 = template("out7: {{ . }}", $out7)
-$t8 = template("out8: {{ . }}", $out8)
+$t1 = golang.template("out1: {{ . }}", $out1)
+$t2 = golang.template("out2: {{ . }}", $out2)
+$t3 = golang.template("out3: {{ . }}", $out3)
+$t4 = golang.template("out4: {{ . }}", $out4)
+$t5 = golang.template("out5: {{ . }}", $out5)
+$t6 = golang.template("out6: {{ . }}", $out6)
+$t7 = golang.template("out7: {{ . }}", $out7)
+$t8 = golang.template("out8: {{ . }}", $out8)
 
 test "${t1}" {}
 test "${t2}" {}

lang/interpret_test/TestAstFunc2/map-iterator2.txtar

@@ -1,4 +1,5 @@
 -- main.mcl --
+import "golang"
 import "iter"
 
 $fn = func($x) { # ignore arg
@@ -9,7 +10,7 @@ $ins = [5, 4, 3, 2, 1,]
 
 $out = iter.map($ins, $fn)
 
-$t = template("out: {{ . }}", $out)
+$t = golang.template("out: {{ . }}", $out)
 
 test "${t}" {}
 -- OUTPUT --

lang/interpret_test/TestAstFunc2/map-iterator3.txtar

@@ -1,4 +1,5 @@
 -- main.mcl --
+import "golang"
 import "iter"
 
 $fn = func($x) { # type changes from str to int
@@ -9,7 +10,7 @@ $ins = ["a", "bb", "ccc", "dddd", "eeeee",]
 
 $out = iter.map($ins, $fn)
 
-$t = template("out: {{ . }}", $out)
+$t = golang.template("out: {{ . }}", $out)
 
 test "${t}" {}
 -- OUTPUT --

lang/interpret_test/TestAstFunc2/map-iterator4.txtar

@@ -1,4 +1,5 @@
 -- main.mcl --
+import "golang"
 import "iter"
 
 $ins = ["a", "bb", "ccc", "dddd", "eeeee",]
@@ -9,7 +10,7 @@ $out = iter.map($ins, func($x) {
 
 })
 
-$t = template("out: {{ . }}", $out)
+$t = golang.template("out: {{ . }}", $out)
 
 test "${t}" {}
 -- OUTPUT --

lang/interpret_test/TestAstFunc2/template-0.txtar

@@ -1,5 +1,6 @@
 -- main.mcl --
 import "datetime"
+import "golang"
 
 $secplus42 = 42 + $ayear
 
@@ -9,7 +10,7 @@ $ayear = 60 * 60 * 24 * 365	# is a year in seconds (31536000)
 $tmplvalues = struct{time => $secplus42, hello => "world",}
 
 print "template-0" {
-	msg => template("Hello: {{ .hello }}, 42 sec + 1 year is: {{ .time }} seconds, aka: {{ datetime_print .time }}", $tmplvalues),
+	msg => golang.template("Hello: {{ .hello }}, 42 sec + 1 year is: {{ .time }} seconds, aka: {{ datetime_print .time }}", $tmplvalues),
 }
 -- OUTPUT --
 Vertex: print[template-0]

lang/interpret_test/TestAstFunc2/template-1.txtar

@@ -1,6 +1,8 @@
 -- main.mcl --
+import "golang"
+
 $v = 42
-$x = template("hello", $v) # redirect var for harder unification
+$x = golang.template("hello", $v) # redirect var for harder unification
 test "${x}" {
 	#anotherstr => $x,
 }

lang/interpret_test/TestAstFunc2/unify-template.txtar

@@ -1,4 +1,5 @@
 -- main.mcl --
+import "golang"
 import "sys"
 
 $tmplvalues = struct{num => 42, load => $theload,}
@@ -7,7 +8,7 @@ $theload bool = sys.load()->x1 # wrong type, make sure the compiler catches it!
 
 file "/tmp/datetime" {
 	state => $const.res.file.state.exists,
-	content => template("num: {{ .num }} seconds\nload average: {{ .load }}\n", $tmplvalues),
+	content => golang.template("num: {{ .num }} seconds\nload average: {{ .load }}\n", $tmplvalues),
 }
 -- OUTPUT --
 # err: errUnify: error setting type: func() { <built-in:_struct_lookup> }, error: field x1 type error: base kind does not match (bool != float)