Make build process compatible with newer versions of NodeJS/npm

[desrosj]

The build scripts and processes currently require NodeJS 14.x and NPM < 7 (6.x).

Some notes:

• NodeJS 14.x is currently in the maintenance phase, which ends April, 30, 2023.
• NodeJS 16.x (the current LTS version) enters the maintenance phase on October 18, 2022.
• NodeJS 18.x enters LTS on October 25, 2022.
• NPM 7 introduces a new lock file format (see #52951).
• NPM 8 had only one notable breaking change, ​dropping support for NodeJS 10.
• Twenty Nineteen, Twenty Twenty, and Twenty Twenty-One all have their own package.json files and are set up to run on NodeJS 14.x. These should probably be updated as well so that the version required is consistent.

[desrosj]

Since 18.x will enter LTS in late October, it may make sense to skip transitioning to 16.x all together. However, it's possible that some dependencies will need a bit more time to release a version that supports 18.x, so a two phase update may also be reasonable.

[desrosj]

#52951 was marked as a duplicate.

[desrosj]

Unfortunately, I haven't had the time to make any progress on this for 6.2.

Going to punt, but to 6.3 as this needs to be done before the maintenance window for 14.x ends in April.

@gziolo is back from his leave, so I'm going to make an effort to tackle this with him in Gutenberg and Core in the coming weeks.

[ironprogrammer]

Noting here that 16.x is scheduled for EOL on September 11, 2023, moved forward seven months sooner, as ​explained in this announcement (​full schedule).