feat(test): create coverage reports when --coverage specified in deno test (#28260)

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)

tests/specs/coverage/default_reports/source.ts

@@ -0,0 +1,9 @@
+/**
+ * @example Usage
+ * ```ts
+ * add(1, 2); // 3
+ * ```
+ */
+export function add(a: number, b: number): number {
+  return a + b;
+}