Possible fix for inline JS being added out of sequence

[hughbris]

Adds a new Assets test assertion to verify order of output per #1893. Fixes asset order by removing default position=after property in newly instantiated inlineJs objects.

Notes/limitations:

• May be incomplete because there are other asset types where position=after is set by default in constructor.
• Not clear if there was a good reason to set position=after by default, or unintended consequences not setting it.
• Not actually clear on the intended purpose of asset position property vs priority.
• Though it's a bug fix restoring expected behaviour, this is a potentially breaking change for existing Grav sites. So might be wise to create a toggle setting in system assets config.

[hughbris]

Converted this to draft PR after reading what that means. With the caveats listed above, I am sure this PR will need changing before it should be pulled.