RFR: 8303039: Utilize `coverageLevels.txt` [v2]

[Naoto Sato]

> This is a pre-requisite for supporting CLDR v43, where they combine `seeds` locales with `common` locales (https://cldr.unicode.org/index/downloads/cldr-43#h.7s25aqdv767e). In order to have the same coverage level of locales, CLDRConverter tool needs to comb through the locale files based on the `coverageLevels.txt` file, (and the ones we already included as of v42). Confirmed the same set of locales is generated before and after this modification.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  Explicitly filter coverage levels

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12812/files
  - new: https://git.openjdk.org/jdk/pull/12812/files/2d0f16f3..8ae9ba61

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12812&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12812&range=00-01

  Stats: 5 lines in 1 file changed: 1 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/12812.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12812/head:pull/12812

PR: https://git.openjdk.org/jdk/pull/12812