pecl8: command not found

Hello, I tried to install package opentelemetry without success.

The pecl extension was not found.

I tried following the manual with the following commands:

```
RUN apk add --no-cache $PHPIZE_DEPS \
&& pecl8 install opentelemetry
```

With the following return:

```
bash-5.1# apk add --no-cache $PHPIZE_DEPS \
&& pecl8 install opentelemetry
fetch https://dl-cdn.alpinelinux.org/alpine/v3.16/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.16/community/x86_64/APKINDEX.tar.gz
OK: 318 MiB in 147 packages
bash: pecl8: command not found
bash-5.1#
```

How to correctly install pecl?

Tks!

Start by reproducing the reported Alpine Docker commands, especially `apk add --no-cache $PHPIZE_DEPS` followed by `pecl8 install opentelemetry`, and inspect the image's PHP version and package setup. Done means the documented container build can locate PECL and install the OpenTelemetry extension successfully.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.