Generate regular expressions for locations during alias_traversal checks

[MegaManSec]

This patch allows us to catch any incorrect alias usage inside location blocks with regex.

It also changes a probably-not-vulnerable report to LOW severity.

[MegaManSec]

Notes:

Not vulnerable:

location ~ /images/(.*) {
  alias /app/static/$1;
}

Not vulnerable:

location ~ /image(s) {
  alias /app/static/;

Note vulnerable:

location ~ /image {
  alias /app/static/;

Vulnerable:

location ~ /images(.*) {
  alias /app/static/$1;
}

Vulnerable:

location ~ /images(.*)/lol {
  alias /app/static/$1;
}

[sonarqubecloud]

Quality Gate failed

Failed conditions
B Maintainability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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