Fixes Dropdown wrong default color

[MV-GH]

According to the m3 specs, dropdown has a 3dp tonal elevation, this was missing and caused the discrepancy between DropdownMenu and CascadeDropdownMenu. See https://m3.material.io/styles/elevation/tokens#df721a00-888e-4c5e-bfe1-5d905f167aaa

After:

8Z8ul9eEY3.mp4

Before:

studio64_ydSz9zlk9O.mp4

Fixes #39

[saket]

Thank you so much!

[saket]

Can you regenerate test screenshots using and add them to this PR?

./gradlew cascade-compose:connectedDebugAndroidTest -Pdropshots.record

[MV-GH]

I generated them using a Pixel 7 API 31.

[MV-GH]

Made some small changes, I saw that it was setting the shadowElevation to the tonalElevation. And made a argument for tonalElevation

[MV-GH]

There was a test with this remark

// Drop shadows are strangely causing tiny differences in
// generated screenshots. A zero elevation is used to avoid this.
private val shadowElevation = 0.dp

This was actually changing the tonalElevation and now it actually changes the shadowElevation

Not sure if this is still needed?

[saket]

I'm sorry this took me some time. trunk has moved ahead so let me land your changes manually.

[saket]

Do you need your popups to have a different shadow and tonal elevations?

[MV-GH]

I don't, but others might and this matches the Compose API as it gives both options

[saket]

Can you point me to that? I don't see any tonalElevation parameter on DropdownMenu():

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/material/material/src/androidMain/kotlin/androidx/compose/material/AndroidMenu.android.kt;l=112;drc=cdd989b146a4758f9974b63c2e53e4eb767e961e

[saket]

Sorry wrong link, here's m3:

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:compose/material3/material3/src/androidMain/kotlin/androidx/compose/material3/AndroidMenu.android.kt;l=84;drc=15aff086d739e6673f71e5cc7bf0d01689942cc6