ci: bump npm to version 7

[villebro]

While the docs state npm@7 to be a requirement for running Superset (see #13100 which migrated to then new lockfile format), CI is still running version 6. It turns out running npm@7 with node@14 isn't very well supported: actions/setup-node#213 . Long term, we should probably bump to node@16 to get rid of this workaround.

When running npm ci on #16701 using npm@6 we get the following error:

$ npm i -g npm@6
$ npm --version
6.14.15
$ npm ci

npm WARN prepare removing existing node_modules/ before installation
npm ERR! watchpack-chokidar2 not accessible from watchpack

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/ville/.npm/_logs/2021-09-20T11_10_20_593Z-debug.log

This is fixed by simply bumping to version 7:

$ npm i -g npm@7
$ npm ci
...
added 3599 packages, and audited 3600 packages in 3m

248 packages are looking for funding
  run `npm fund` for details

79 vulnerabilities (11 low, 22 moderate, 46 high)

To address issues that do not require attention, run:
  npm audit fix

To address all issues possible (including breaking changes), run:
  npm audit fix --force

Some issues need review, and may require choosing
a different dependency.

Run `npm audit` for details.

After this update, CI uses npm@7:

SUMMARY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[villebro]

Adding changes in bashlib.sh to flag frontend changes, as this file controls many aspects of how dependencies are managed on CI.

[codecov]

Codecov Report

Merging #16748 (a4f7bda) into master (985aa06) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #16748   +/-   ##
=======================================
  Coverage   76.86%   76.86%           
=======================================
  Files        1007     1007           
  Lines       54174    54174           
  Branches     7463     7463           
=======================================
  Hits        41639    41639           
  Misses      12295    12295           
  Partials      240      240           

Flag	Coverage Δ
javascript	71.30% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 985aa06...a4f7bda. Read the comment docs.