fix: install extensions under remote user not root user #67

Job	Run time
test-autogenerated (code-server, debian:latest)	1m 9s
test-docs	6s
test-global	7s
test-scenarios (code-server)	21m 28s
test-autogenerated (code-server, mcr.microsoft.com/devcontainers/base:ubuntu)	1m 25s
test-autogenerated (code-server, fedora:latest)	1m 12s
test-autogenerated (code-server, ubuntu:latest)	1m 25s
	26m 52s

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