docs: update installation guide

[nitishfy]

Description

Generally, when you're trying to install the apisix from the installation guide, sometimes you come across the Address Bind already in use error logs when trying to start the apisix server. This is likely caused due to the unavailability of the port. Mostly, it happens if you've installed the apisix using docker due to which the ports get equipped. Hence, when you try installing the apisix locally, you get the error logs.

This PR mentions this minor information with solution to this problem. There is a little refactoring of the docs as well. Since, it is required to install the etcd first, the installation part of etcd is moved first, followed by installation of apisix server installation.

Fixes # (issue)

Checklist

• [x] I have explained the need for this PR and the problem it solves
• [ ] I have explained the changes or the new features added to this PR
• [ ] I have added tests corresponding to this change
• [x] I have updated the documentation to reflect this change
• [x] I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[nitishfy]

The linter issues have been fixed now

[kayx23]

Do we need this PR still? The most beneficial change here as it seems is to re-arrange etcd and APISIX installation order.

Let's re-align what needs to be done here and move this effort forward. Thanks.

[kayx23]

🏓

[kayx23]

The only change beneficial here is to adjust the order of APISIX and etcd installation. This can be addressed in a separate PR. Closing this PR as it is stagnant.