mojo: Rename lite JS bindings

See https://docs.google.com/document/d/1RB1F4ym02avbwuLMEQ_un8CQ4bPMcfO7H8St5-NRmq0/edit#

Adds a "use_old_js_lite_bindings_names" variable whose default value is true.
A follow up CL will make its default false and change all current users of
the old names to manually set the flag to true.

Bug: 968369
Change-Id: I84cbe8824f15e9bf58339403481390ca29a98abe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1686589
Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#675496}

• BUILD.gn[diff]
• content/shell/BUILD.gn[diff]
• content/test/BUILD.gn[diff]
• content/test/data/lite_js_old_names_test.mojom[Added - diff]
• mojo/public/tools/bindings/generators/js_templates/lite/interface_definition.tmpl[diff]
• mojo/public/tools/bindings/generators/mojom_js_generator.py[diff]
• mojo/public/tools/bindings/mojom.gni[diff]
• mojo/public/tools/bindings/mojom_bindings_generator.py[diff]
• mojo/public/tools/bindings/pylib/mojom/generate/generator.py[diff]
• third_party/blink/web_tests/mojo/bindings-lite-old-names.html[Added - diff]
• third_party/blink/web_tests/mojo/bindings-lite.html[diff]