Merge pull request dotnet/coreclr#1744 from Priya91/palstring-rest

Use StackString in PAL file apis.

Commit migrated from https://github.com/dotnet/coreclr/commit/6b091902c7f2cc2578a8fb34a7ce8115f0f9cb8b

diff --cc src/coreclr/src/pal/src/file/find.cpp
Simple merge

diff --cc src/coreclr/src/pal/src/file/path.cpp
Simple merge

diff --cc src/coreclr/src/pal/src/loader/module.cpp
Simple merge

diff --cc src/coreclr/src/pal/src/misc/perftrace.cpp
Simple merge

diff --cc src/coreclr/src/pal/src/synchmgr/synchmanager.cpp
Simple merge

diff --cc src/coreclr/src/pal/src/thread/process.cpp
Simple merge