feat(test): create coverage reports when --coverage specified in deno test

[kt3k]

part of #21325
closes #28218

This PR updates the behavior of deno test --coverage option. Now if --coverage option is specified, deno test command automatically shows summary report in the terminal, and generates the lcov report in $coverage_dir/lcov.info and html report in $coverage_dir/html/

This change also adds --coverage-raw-data-only flag, which prevents the above reports generated, instead only generates the raw json coverage data (which is the same as current behavior)

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An example of execution looks like:

$ deno test --coverage
running 41 tests from ./yaml/parse_test.ts
parse() handles single document yaml string ... ok (2ms)
parseAll() handles yaml string with multiple documents ... ok (0ms)
parse() throws with `!!js/*` yaml types with default schemas ... ok (0ms)

... snip ...

stringify() handles undefined object entry with skipInvalid and flowLevel option ... ok (0ms)
stringify() handles undefined object entry with big key and skipInvalid and flowLevel option ... ok (0ms)
stringify() handles duplicate binary references ... ok (0ms)

ok | 83 passed | 0 failed (442ms)

-----------------------------------------------------
File                            | Branch % | Line % |
-----------------------------------------------------
 assert/almost_equals.ts        |    100.0 |    4.5 |
 assert/array_includes.ts       |    100.0 |   10.3 |
 assert/assert.ts               |      0.0 |   50.0 |

... snip ...

 yaml/_utils.ts                 |    100.0 |  100.0 |
 yaml/parse.ts                  |    100.0 |  100.0 |
 yaml/stringify.ts              |    100.0 |  100.0 |
-----------------------------------------------------
 All files                      |     86.9 |   54.1 |
-----------------------------------------------------
Lcov coverage report has been generated at file:///Users/kt3k/denoland/std/coverage/lcov.info
HTML coverage report has been generated at file:///Users/kt3k/denoland/std/coverage/html/index.html

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Note: jest --coverage outputs 'summary' and 'lcov' reports by default. This outputs 'html' reports in addition to them.

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Planning to land for Deno 2.3

[bartlomieju]

I think this is a good idea 👍

[bartlomieju]

I believe this function should remove previously generated coverage before dumping new reports to the directory. Otherwise the results might be skewed from previous runs. WDYT?

[kt3k]

Updated. Now deno test --coverage clears the reports & raw data from the previous runs. It still keeps the contents of coverage_dir when --coverage-raw-data-only specified (and --clean not specified) to support the advanced scenarios.

[bartlomieju]

This unwrap is sus here 😬 maybe consider failing gracefully with an error message? Also you don't need to do the conversion to string first - Url::from_file_path will accept a PathBuf

[kt3k]

Updated. Now it prints error message when .canonicalize failed