Support having multiple values in Attribute

[syoyo]

Currently TinyUSDZ's Attribute/Property implementation does not allow having multiple values(the first wins)

USD's Attribute can have multiple values(default value, timeSamples and connection)

https://lucascheller.github.io/VFX-UsdSurvivalGuide/core/elements/animation.html

we need to support a syntax like this.
This would change TinyUSDZ's API

def Cube "Cube" (
)
{
    double size = 15
    double size.timeSamples = {
        1001: 1,
        1010: 10,
    }
   double size.connection = </path/to/value>
}

[syoyo]

NOTE

timeSamples and connect seems not able to have attribute metadata

def Cube "Cube" (
)
{
    double size = 15 ( a = 3 ) # ok
    double size.timeSamples = {
        1001: 1,
        1010: 10,
    } ( a = 4) # fail
   double size.connection = </path/to/value> ( a = 5 ) # fail
}

[syoyo]

working branch: https://github.com/syoyo/tinyusdz/tree/multi-value-prop

[syoyo]

Added workaround to co-exist default value and timesamples in rendermesh-refactor branch: bdedcc0

[multi-value-prop](https://github.com/syoyo/tinyusdz/tree/multi-value-prop) branch need to taking into account with this workaround when merging.

[syoyo]

Work items

• Support parsing multi value for Attribute in USDA parser 0c147e5
• Support parsing multi value for Attribute in USDC parser 0902c19
• Support handling multi-value Attribute in PrimReconstruct
• Support handling multi-value Attribute in Tydra EvaluateAttribute

[syoyo]

Supported via d7eb9da