Extract parameter name without any firm pattern.

We want to extract everything that `NAME` contains in (`$param.<NAME> | $param.<NAME>[*]`)
or (`param["<NAME>"] | $param["<NAME>"][*]`) or (`param['NAME'][*] | $param['<NAME>'][*]`).
We dont want to enforce the pattern that it should follow. That part should be done by
`Step 1` in #4799 (comment)

The regex pattern substitution `.*?(\[\*\])?` matches and extracts everything that is
contained in `<NAME>` or `<NAME>[*]`.

pkg/substitution/substitution.go

@@ -25,8 +25,7 @@ import (
 	"knative.dev/pkg/apis"
 )
 
-const parameterSubstitution = `[_a-zA-Z][_a-zA-Z0-9.-]*(\[\*\])?`
-
+const parameterSubstitution = `.*?(\[\*\])?`
 const braceMatchingRegex = "(\\$(\\(%s(\\.(?P<var1>%s)|\\[\"(?P<var2>%s)\"\\]|\\['(?P<var3>%s)'\\])\\)))"
 
 // ValidateVariable makes sure all variables in the provided string are known