Allow controlling GC zeal via JS_GC_ZEAL environment variable.
Move stack roots into Root types instead of RootCollection, removing the aribtrary 10 roots per stack frame restriction.
s/Unrooted/Temporary/g
Root Temporary values for the duration of their lifetime.
Store per-ScriptTask RootCollection in TLS and use that in favour of per-frame collections.
Remove all root collections.
Address review comments.