[bundle optimization] Update to semver 7.x to get tree-shaking (#83020) (#83542)
## What's changed in this PR
### Update to latest available `semver`: `7.3.2`
* `semver` 5.x pulls in the entire library in one large file (~38k uncompressed / ~9k gz), when we might only use 1-2K.
* `semver` 7.0+ supports tree-shaking: https://github.com/npm/node-semver/blob/master/CHANGELOG.md#700
### Update paths to only import individual function(s) used instead of the entire library
* Getting the smaller bundle requires a different import style [as shown in the docs](https://github.com/npm/node-semver#usage)
* Only changed code in `public` & `common` folders; not `server`. We could also update `server` as well for consistency, but I skipped because the new import style is more verbose and the filesize didn't seem as important on the server
### Results
The build stats show a 10K+ improvement for initial page bundles https://github.com/elastic/kibana/pull/83020#issuecomment-724724432
| id | [before](c6afc47f32) | [after](213bb52a8c) | diff |
| --- | --- | --- | --- |
| `ingestManager` | 386.2KB | 373.9KB | -12.3KB |
| `telemetry` | 63.5KB | 50.1KB | -13.5KB |
| `upgradeAssistant` | 74.5KB | 60.5KB | -14.0KB |
| total | | | -39.7KB |
### The import paths look odd. Are they required?
I agree and, no, they're not strictly required. If you'd like me to revert to the prior style just drop a comment and I'll undo them.
The caveat is that the current style (in `master` & this PR) pulls in the entire `semver` library. In 7.x that added ~15K to the initial size. Some more details in the comments: https://github.com/elastic/kibana/pull/83020#issuecomment-724859130
### Possible issues
Moving 2 major versions. We're currently on 5.7 and the latest available is 7.3.
* changelog says 5.x (our current) to 6.0 should be safe: https://github.com/npm/node-semver/blob/master/CHANGELOG.md#60
* There 6.x & 7.x changes all appear to be new features or bugfixes around the `includePrerelease` flag added in 5.6, but I'm not sure if those "fixes" will break existing code
* https://github.com/npm/node-semver/blob/master/CHANGELOG.md#613
* https://github.com/npm/node-semver/blob/master/CHANGELOG.md#722
### Stats / screenshots
generated with `node scripts/build_kibana_platform_plugins.js --profile --focus=ingestManager`
<details><summary><b>Ingest Manager in `master`</b>: imports entire `semver` lib, totals 40k+, only 1 large file (orange arc below)</summary>
<img width="972" alt="Screen Shot 2020-11-09 at 6 50 23 PM" src="https://user-images.githubusercontent.com/57655/98666188-a50ac380-231a-11eb-9b8a-6ca784752714.png">
</details>
<details><summary><b>Ingest Manager in PR after upgrade to 7</b>: still imports entire lib. file size *increased* to ~60k, but now individual files are imported (orange arcs below)</summary>
<img width="825" alt="Screen Shot 2020-11-09 at 5 46 30 PM" src="https://user-images.githubusercontent.com/57655/98666355-e602d800-231a-11eb-803f-bc04beb4eaf1.png">
<img width="963" alt="Screen Shot 2020-11-09 at 5 47 06 PM" src="https://user-images.githubusercontent.com/57655/98666357-e69b6e80-231a-11eb-92d3-c66904f92c30.png">
</details>
<details><summary><b>Ingest Manager in PR after changing `import`s:</b> total imported size down to ~20k. Can see individual imported files</summary>
<img width="926" alt="Screen Shot 2020-11-10 at 6 10 23 AM" src="https://user-images.githubusercontent.com/57655/98667058-e64fa300-231b-11eb-9690-5e36ed6475e0.png">
<img width="895" alt="Screen Shot 2020-11-10 at 6 10 53 AM" src="https://user-images.githubusercontent.com/57655/98667059-e780d000-231b-11eb-8abf-98d8bdbcf061.png">
</details>
### Checklist
- [ ] [Unit or functional tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html) were updated or added to match the most common scenarios
b2a7efe371
