- Show strings with escaping, rather than trying to output the text
unmodified.
- Show symbols with the same formatting as Strings
- Avoid accidentally defining a broken Core.show method for NamedTuple

Makes more types survive `jl_static_show` unambiguously:
- Symbols
- Symbols printed in the `:var"foo"` form use raw string escaping,
fixing `:var"a\b"`, `:var"a\\"`, `:var"$a"`, etc.
  - Symbols that require parens use parens (`:(=)`, ...)
- Signed integers: Except for `Int`, signed integers print like
`Int8(1)`.
- Floats: floats are printed in a naive but reversible (TODO: double
check) way. `Inf(16|32|)` and `NaN(16|32|)` are printed, and
`Float16`/`Float32` print the type (`Float32(1.5)`). `Float64`s are
printed with a trailing `.0` if it is necessary to disambiguate from
`Int`.

Fixes JuliaLang#52677,
JuliaLang#58484 (comment),
JuliaLang#58484 (comment),
and the specific case mentioned in JuliaLang#58484. Improves the situation for
round-trip (inexhaustive list):
- Non-canonical NaNs
- BFloat16
- User-defined primitive types. This one is tricky, because they can
have a size different from any type we have literals for.