Improve TOML error reporting by including line numbers

Description

A customer encountered an error in their config.toml when installing with the --user flag:

gitlab-runner install --user=gitlab-runner
Runtime platform arch=amd64 os=linux pid=56174 revision=f188edd7 version=14.9.1
FATAL: toml: cannot load TOML value of type map[string]interface {} into a Go string

Since the specific line number isn't logged, this can make it tedious to troubleshoot exactly what's wrong in the config.toml.

Reference ticket: US Federal Ticket (Internal access to verified US Citizens only)

Proposal

TOML package has the ability to log the specific line and column of the error using ErrorWithLocation().

Links to related issues and merge requests / references

#3226 (closed)