This commit adds "--output" to "deno coverage" subcommand.
It can be used instead of piping output to a file.
Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>
Covered ranges were not merged and thus it appeared that some lines
might be uncovered. To fix this I used "v8-coverage" that takes care
of merging the ranges properly. With this change, coverage collected
from a file by multiple entrypoints is now correctly calculated.
I ended up forking https://github.com/demurgos/v8-coverage and adding
"cli/tools/coverage/merge.rs" and "cli/tools/coverage/range_tree.rs".
