lib: introduce `forEach` = flip map (#64723)

* lib: introduce `foreach` = flip map

The main purpose is to bring attention to `flip map`, which improves
code readablity. It is useful when ad-hoc anonymous function
grows two or more lines in `map` application:

```
      map (lcfg:
        let port = lcfg.port;
            portStr = if port != defaultPort then ":${toString port}" else "";
            scheme = if cfg.enableSSL then "https" else "http";
        in "${scheme}://cfg.hostName${portStr}"
      ) (getListen cfg);
```
Compare this to `foreach`-style:
```
      foreach (getListen cfg) (lcfg:
        let port = lcfg.port;
            portStr = if port != defaultPort then ":${toString port}" else "";
            scheme = if cfg.enableSSL then "https" else "http";
        in "${scheme}://cfg.hostName${portStr}"
      );
```
This is similar to Haskell's `for` (http://hackage.haskell.org/package/base-4.12.0.0/docs/Data-Traversable.html#v:for)

* mass replace "flip map -> foreach"

See `foreach`-introduction commit.
```
rg 'flip map ' --files-with-matches | xargs sed -i 's/flip map /foreach /g'
```

* Revert "mass replace "flip map -> foreach""

This reverts commit 3b0534310c89d04fc3a9c5714b5a4d0f9fb0efca.

* mass replace "flip map -> forEach"

See `forEach`-introduction commit.
```
rg 'flip map ' --files-with-matches | xargs sed -i 's/flip map /forEach /g'
```

* rename foreach -> forEach

* and one more place

* add release notes

0 files changed, 0 insertions, 0 deletions