Register nowarn when inlining

[som-snytt]

Fixes #22672

"Register" @nowarn annotations on inlined methods and also on expressions in inlined bodies.

registerNoWarn is refactored to run.suppressions for ease of use.

[som-snytt]

It should be selective, since it's not necessary under joint compilation.

Also, I didn't look at why -Werror did not error on the ticket.

[lrytz]

I assume deprecates are reported because they are handled in a phase after inlining, while other warnings are not issued because they are issued before? That seems arbitrary.

scala> inline def foo = { 1; Stream(1).head }
2 warnings found
-- [E129] Potential Issue Warning: ---------------------------------------------
1 |inline def foo = { 1; Stream(1).head }
  |                   ^
  |                   A pure expression does nothing in statement position
  |
  | longer explanation available when compiling with `-explain`
-- Deprecation Warning: --------------------------------------------------------
1 |inline def foo = { 1; Stream(1).head }
  |                      ^^^^^^
  |value Stream in package scala is deprecated since 2.13.0: Use LazyList instead of Stream
def foo: Int

scala> foo
1 warning found
-- Deprecation Warning: --------------------------------------------------------
1 |inline def foo = { 1; Stream(1).head }
  |                      ^^^^^^
  |value Stream in package scala is deprecated since 2.13.0: Use LazyList instead of Stream
val res0: Int = 1

scala>

Is there ever a good reason to issue warnings in inlined code?

[som-snytt]

@lrytz I haven't crafted the test yet, but it could summon a deprecated given.