[PHP] Fix message for InvalidArgumentException(), when failing to test pattern

[thomasphansen]

model_generic.mustache: Display property name instead of its value, when throwing InvalidArgumentException() for values not respecting a given pattern.

This is an old annoying bug: in 2016 the error message for this InvalidArgumentException() mas changed from single to double quotes, to allow patterns containing single quotes. This caused the "$" sign (plus the following property name) to be parsed, making the error message display its content, instead of its name (like in all other exception messages in this file). This PR fixes that by escaping the "$" sign.

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[wing328]

@thomasphansen thanks for the PR, which looks good to me.