Rollup merge of #90833 - tmiasko:optimization-remarks, r=nikic

Rollup merge of #90833 - tmiasko:optimization-remarks, r=nikic

Emit LLVM optimization remarks when enabled with `-Cremark`

The default diagnostic handler considers all remarks to be disabled by
default unless configured otherwise through LLVM internal flags:
`-pass-remarks`, `-pass-remarks-missed`, and `-pass-remarks-analysis`.
This behaviour makes `-Cremark` ineffective on its own.

Fix this by configuring a custom diagnostic handler that enables
optimization remarks based on the value of `-Cremark` option. With
`-Cremark=all` enabling all remarks.

Fixes #90924.

r? `@nikic`