[flang] Do not resolve TRIM/REPEAT length to its argument length

For TRIM and REPEAT calls, semantics was creating ProcedureDesignators
using the length parameter of the arguments. This caused bugs when
folding LEN(TRIM(char_explicit_constant_length)). The same did not
appeared in folding for REPEAT because it is rewritten at a higher
level to LEN(c)*N.

This is not only a folding issue since any place (like lowering) may
try to use the bad length parameter from the created ProcedureDesignator.

Update intrinsic resolution to not copy the length parameter for TRIM
and REPEAT.

Differential Revision: https://reviews.llvm.org/D134970