lib: rename js source to lower snake_case

[danbev]

This commit renames all JavaScript source files in lib to lower snake_case.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[devsnek]

in https://github.com/nodejs/node/tree/master/lib/internal/modules/esm everything is named in that style, i suppose they should also be renamed?

[TimothyGu]

There is also https://github.com/nodejs/node/blob/master/lib/internal/vm/Module.js.

[vkurchatkin]

It is named like this because it exports a single class.

[danbev]

It is named like this because it exports a single class.

I did notice this and that is why I brought it up. Do we want to keep it like this or should we rename all JavaScript source files to lowercase? (I'd prefer to rename)

[devsnek]

i've had enough trouble with caseless filesystems to wholeheartedly recommend keeping everything as snake_case

[danbev]

Rebased CI: https://ci.nodejs.org/job/node-test-pull-request/13868/

[danbev]

node-test-commit-linuxone failure looks unrelated

console output:

Building addon /data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/test/addons-napi/test_function/
if [ -x /data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/./node ] && [ -e /data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/./node ]; then /data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/./node  tools/doc/generate.js --format=json doc/api/cluster.md > out/doc/api/cluster.json; elif [ -x `which node` ] && [ -e `which node` ] && [ `which node` ]; then `which node`  tools/doc/generate.js --format=json doc/api/cluster.md > out/doc/api/cluster.json; else echo "No available node, cannot run \"node  tools/doc/generate.js --format=json doc/api/cluster.md > out/doc/api/cluster.json\""; exit 1; fi;
  SOLINK_MODULE(target) Release/obj.target/binding.node
  COPY Release/binding.node
make[2]: Leaving directory `/data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/test/addons/hello-world/build'
make[2]: write error
gyp ERR! build error 
gyp ERR! stack Error: `make` failed with exit code: 1
gyp ERR! stack     at ChildProcess.onExit (/data/iojs/build/workspace/node-test-commit-linuxone/nodes/rhel72-s390x/deps/npm/node_modules/node-gyp/lib/build.js:258:23)
gyp ERR! stackmake[1]: gyp info it worked if it ends with ok

[trivikr]

This code looks good to land

[danbev]

Landed in f2b1079.

[targos]

Should this be backported to v9.x-staging? If yes please follow the guide and raise a backport PR, if not let me know or add the dont-land-on label.