This commit removes unnecessary conversion into BTreeMap. The value
that gets converted into BTreeMap is _originally_ BTreeMap, so this
conversion is just superfluous.
Additionally, a test is added so that we can make sure the keys in the
emitted lockfile are sorted alphabetically.
This commit fixes problems with source maps in Chrome Devtools
by substituting source map URL generated by TS compiler with
actual file URL pointing to DENO_DIR.
Dummy value of "source_map_url" has been removed from
"ScriptOrigin".
Also fixes lock file which used compiled source code to generate
lock hash; it now uses source code of the file that is
being compiled.
