Server-side syntax highlighting for all code (#12047)

* Server-side syntax hilighting for all code

This PR does a few things:

* Remove all traces of highlight.js
* Use chroma library to provide fast syntax hilighting directly on the server
* Provide syntax hilighting for diffs
* Re-style both unified and split diffs views
* Add custom syntax hilighting styling for both regular and arc-green

Fixes #7729
Fixes #10157
Fixes #11825
Fixes #7728
Fixes #3872
Fixes #3682

And perhaps gets closer to #9553

* fix line marker

* fix repo search

* Fix single line select

* properly load settings

* npm uninstall highlight.js

* review suggestion

* code review

* forgot to call function

* fix test

* Apply suggestions from code review

suggestions from @silverwind thanks

Co-authored-by: silverwind <me@silverwind.io>

* code review

* copy/paste error

* Use const for highlight size limit

* Update web_src/less/_repository.less

Co-authored-by: Lauris BH <lauris@nix.lv>

* update size limit to 1MB and other styling tweaks

* fix highlighting for certain diff sections

* fix test

* add worker back as suggested

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

vendor/github.com/alecthomas/chroma/lexers/a/apl.go

@@ -0,0 +1,36 @@
+package a
+
+import (
+	. "github.com/alecthomas/chroma" // nolint
+	"github.com/alecthomas/chroma/lexers/internal"
+)
+
+// Apl lexer.
+var Apl = internal.Register(MustNewLexer(
+	&Config{
+		Name:      "APL",
+		Aliases:   []string{"apl"},
+		Filenames: []string{"*.apl"},
+		MimeTypes: []string{},
+	},
+	Rules{
+		"root": {
+			{`\s+`, Text, nil},
+			{`[⍝#].*$`, CommentSingle, nil},
+			{`\'((\'\')|[^\'])*\'`, LiteralStringSingle, nil},
+			{`"(("")|[^"])*"`, LiteralStringDouble, nil},
+			{`[⋄◇()]`, Punctuation, nil},
+			{`[\[\];]`, LiteralStringRegex, nil},
+			{`⎕[A-Za-zΔ∆⍙][A-Za-zΔ∆⍙_¯0-9]*`, NameFunction, nil},
+			{`[A-Za-zΔ∆⍙][A-Za-zΔ∆⍙_¯0-9]*`, NameVariable, nil},
+			{`¯?(0[Xx][0-9A-Fa-f]+|[0-9]*\.?[0-9]+([Ee][+¯]?[0-9]+)?|¯|∞)([Jj]¯?(0[Xx][0-9A-Fa-f]+|[0-9]*\.?[0-9]+([Ee][+¯]?[0-9]+)?|¯|∞))?`, LiteralNumber, nil},
+			{`[\.\\/⌿⍀¨⍣⍨⍠⍤∘]`, NameAttribute, nil},
+			{`[+\-×÷⌈⌊∣|⍳?*⍟○!⌹<≤=>≥≠≡≢∊⍷∪∩~∨∧⍱⍲⍴,⍪⌽⊖⍉↑↓⊂⊃⌷⍋⍒⊤⊥⍕⍎⊣⊢⍁⍂≈⌸⍯↗]`, Operator, nil},
+			{`⍬`, NameConstant, nil},
+			{`[⎕⍞]`, NameVariableGlobal, nil},
+			{`[←→]`, KeywordDeclaration, nil},
+			{`[⍺⍵⍶⍹∇:]`, NameBuiltinPseudo, nil},
+			{`[{}]`, KeywordType, nil},
+		},
+	},
+))