fixes#25718
This pull request optimizes sequence allocation in the Nim standard
library by introducing a way to create uninitialized sequence payloads
for element types that don't require zero-initialization. The changes
allow for more efficient memory allocation when initializing sequences
with types that have no references, avoiding unnecessary zeroing of
memory.
Sequence allocation and initialization improvements:
* Added the `newSeqUninitRaw` procedure to create sequence payloads with
a specified length without forcing zero-initialization for element types
marked as `ntfNoRefs`. (`lib/system/sysstr.nim`,
[lib/system/sysstr.nimR277-R292](diffhunk://#diff-bcaa1967f436ad03877f353823c08a8b4a719fe387629d33aab4bddf16534b5eR277-R292))
* Modified the `extendCapacityRaw` procedure and the `setLengthSeqImpl`
template to use `newSeqUninitRaw` when zero-initialization is not
required, controlled by the `doInit` static parameter.
(`lib/system/sysstr.nim`,
[[1]](diffhunk://#diff-bcaa1967f436ad03877f353823c08a8b4a719fe387629d33aab4bddf16534b5eR277-R292)
[[2]](diffhunk://#diff-bcaa1967f436ad03877f353823c08a8b4a719fe387629d33aab4bddf16534b5eL316-R335)
5948dbbeed