Use ASAR

[alexdima]

Fixes #41350.

This change currently makes it that a node_modules.asar is picked up if present.

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To run with asar, one must take a built version of vscode from this branch and execute:

asar pack node_modules node_modules.asar --unpack {*.node,*.exe}

Then, the node_modules folder can be deleted.

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Observed time improvements (average of 5 runs, excluding first start):

Surface Book with Windows 10

TIME	BEFORE	AFTER	DELTA
[main, renderer] start => extensions ready	1852.2	1766.4	85.8 ms (4.63%)
[main, renderer] start => workbench ready	1707.6	1652.4	55.2 ms (3.23%)

Lenovo W530 with Ubuntu 16.04 TLS

TIME	BEFORE	AFTER	DELTA
[main, renderer] start => extensions ready	1580.4	1555.0	25.40 ms (1.61%)
[main, renderer] start => workbench ready	1313.0	1299.4	13.60 ms (1.04%)

File count reduction:

OS	BEFORE	AFTER	DELTA
Windows	5,817	4,336	1,481 (-25.45%)
Linux	6,341	4,289	2,052 (-32.36%)

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TODO:

• searching is broken due to rg path being node_modules.asar.unpacked and not node_modules.asar.
• incorporate the asar creation into the packaging gulp task.

[jens1o]

I think this is important, because the installation will be a lot faster, even though the improvement by itself is tiny.