Improve MiniPlaceholders support, code improvements, update XSeries to fix 1.21.4 errors and fix MineSkin API keys.

Changes
d5d8613 This commit marks release 15.5.1
7bfb35c Do not use jitpack artifact
2fe82e3 Inline
d304781 Use message for canSetSkin
6a91805 Simplify api calls
b4a87a3 Fix miniplaceholders plugin id
ef4b582 Remake property getter code
e23020f Avoid shadowing more than needed
3fc80d8 Fixup miniplaceholders support by targeting shadowed version directly in code
60f8e29 Fix MineSkin API key ( #1855)

08fc718 Avoid passing audience

Updated dependency:
f62724c Bump to XSeries release
cb920ff Update plugin com.gradle.develocity to v3.19 ( #1856)
f6cbf8d Switch to experimental XSeries

Translations:
6a23497 New Crowdin updates ( #1853)
69271e1 New translations locale.json (Tatar) ( #1858)
c31f85a New translations locale.json (Polish) ( #1854)