prism_compile.c: use rb_enc_interned_str to reduce allocations

The `rb_fstring(rb_enc_str_new())` pattern is inefficient because:

- It passes a mutable string to `rb_fstring` so if it has to be interned it will first be duped.
- It an equivalent interned string already exists, we allocated the string for nothing.

With `rb_enc_interned_str` we either directly get the pre-existing string with 0 allocations,
or efficiently directly intern the one we create without first duping it.

0 files changed, 0 insertions, 0 deletions