STRWEB-87 replace @babel packages that have moved from proposed to official

[BogdanDenis]

Description

From ticket description:

Summary: Use official plugin names for syntax extensions that moved from "proposed" to "official", e.g. plugin-proposal-private-methods is now plugin-tranform-private-methods. 

Details: we reference several libraries in webpack/babel-options.js that previously were provided by @babel/preset-env. Technically, we should always have included them in our package.json as direct dependencies, but since @babel/preset-env also depended on them we never noticed they were missing. Recently, however, babel replaced many of instances of @babel/plugin-proposal-foo with @babel/plugin-transform-foo, causing STRWEB-86. We added these missing dependencies to correct this omission, but the Even More Correct fix is to update both babel-options.js and package.json to use the new, official transforms instead of the old, proposed transforms.

Issues

STRWEB-87

[github-actions]

Jest Unit Test Statistics

0 tests  ±0   0 ✔️ ±0   0s ⏱️ ±0s
0 suites ±0   0 💤 ±0 
0 files   ±0   0 ❌ ±0 

Results for commit 9fa6559. ± Comparison against base commit cbbc3d7.

[github-actions]

BigTest Unit Test Statistics

73 tests  ±0   73 ✔️ ±0   0s ⏱️ ±0s
39 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit 9fa6559. ± Comparison against base commit cbbc3d7.