fix: find-node.sh now respects .nvmrc (#32712)

Summary:
React-native Xcode build steps (such as "Build JS Bundle") rely on `find.node-sh` to find the correct node binary, using nvm if present. We do this because Xcode may run build steps in a fresh shell environment, presumably for repeatable builds.

This PR fixes `find-node.sh`, to respect any `.nvmrc` file that may be present in the build environment.

Today: `find-node.sh` will set the shell environment to the system node version, and ignores any `.nvmrc` the project may provide to pin node for repeatable builds. By ignoring `.nvmrc`, node versions may differ depending on system environment — between developer laptops, or between developer and CI environments. 😞

This problem has been been noticed before in #8887

### Should this fix happen upstream?

Unfortunately this nvm behavior [is intended](nvm-sh/nvm#2053),  for backwards compatibility

## Changelog

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[iOS] [Fixed] - find-node.sh now respects .nvmrc

Pull Request resolved: #32712

Test Plan:
Before:
```bash
# nvm isn't loaded
$ which nvm

# we're on default system node
$ which node && node --version
/usr/local/bin/node
v17.0.1

$ echo v16.13.0 > .nvmrc
$ source ./scripts/find-node.sh

# Expected: v16.13.0
$ node --version
v17.0.1
```

After:
```bash
# we're on default system node
$ which node && node --version
/usr/local/bin/node
v17.0.1

$ echo v16.13.0 > .nvmrc
$ source ./scripts/find-node.sh

# Expected: v16.13.0
$ node --version
v16.13.0
```

After (no .nvmrc, should preserve previous behavior):
```bash
# we're on default system node
$ which node && node --version
/usr/local/bin/node
v17.0.1

$ source ./scripts/find-node.sh

$  nvm ls|grep default
default -> v14.17.1

# Expected: v14.17.1
$ node --version
v14.17.1
```

Reviewed By: sota000

Differential Revision: D32889629

Pulled By: ShikaSD

fbshipit-source-id: 527384055e303a87bad43413fb66a7fd117d1a63

scripts/find-node.sh

@@ -19,12 +19,16 @@ fi
 # Define NVM_DIR and source the nvm.sh setup script
 [ -z "$NVM_DIR" ] && export NVM_DIR="$HOME/.nvm"
 
+# Source nvm with '--no-use' and then `nvm use` to respect .nvmrc
+# See: https://github.com/nvm-sh/nvm/issues/2053
 if [[ -s "$HOME/.nvm/nvm.sh" ]]; then
   # shellcheck source=/dev/null
-  . "$HOME/.nvm/nvm.sh"
+  . "$HOME/.nvm/nvm.sh" --no-use
+  nvm use 2> /dev/null || nvm use default
 elif [[ -x "$(command -v brew)" && -s "$(brew --prefix nvm)/nvm.sh" ]]; then
   # shellcheck source=/dev/null
-  . "$(brew --prefix nvm)/nvm.sh"
+  . "$(brew --prefix nvm)/nvm.sh" --no-use
+  nvm use 2> /dev/null || nvm use default
 fi
 
 # Set up the nodenv node version manager if present