Merge #17507: random: mark RandAddPeriodic and SeedPeriodic as noexcept

55b2cb199c random: mark RandAddPeriodic and SeedPeriodic as noexcept (fanquake)
461e547877 doc: correct random.h docs after #17270 (fanquake)

Pull request description:

  The usage of `MilliSleep()` in SeedPeriodic (previously SeedSleep) was
  [removed](d61f2bb076) in #17270, meaning it, and its users can now be marked `noexcept`.

  This also corrects the docs in random.h for some of the changes in #17270.

ACKs for top commit:
  practicalswift:
    ACK 55b2cb199c
  laanwj:
    ACK 55b2cb199c
  sipa:
    ACK 55b2cb199c

Tree-SHA512: 672d369796e7c4f9b4d98dc545e5454999fa1bef373871994a26041d6163c58909e2255e4f820d3ef011679aa3392754eb57477306a89f5fd3d57e2bd7f0811a

src/random.h

@@ -40,17 +40,17 @@
  *   These entropy sources are slower, but designed to make sure the RNG state contains
  *   fresh data that is unpredictable to attackers.
  *
- * - RandAddSeedSleep() seeds everything that fast seeding includes, but additionally:
- *   - A high-precision timestamp before and after sleeping 1ms.
- *   - (On Windows) Once every 10 minutes, performance monitoring data from the OS.
- -   - Once every minute, strengthen the entropy for 10 ms using repeated SHA512.
- *   These just exploit the fact the system is idle to improve the quality of the RNG
- *   slightly.
+ * - RandAddPeriodic() seeds everything that fast seeding includes, but additionally:
+ *   - A high-precision timestamp
+ *   - Dynamic environment data (performance monitoring, ...)
+ *   - Strengthen the entropy for 10 ms using repeated SHA512.
+ *   This is run once every minute.
  *
  * On first use of the RNG (regardless of what function is called first), all entropy
  * sources used in the 'slow' seeder are included, but also:
  * - 256 bits from the hardware RNG (rdseed or rdrand) when available.
- * - (On Windows) Performance monitoring data from the OS.
+ * - Dynamic environment data (performance monitoring, ...)
+ * - Static environment data
  * - Strengthen the entropy for 100 ms using repeated SHA512.
  *
  * When mixing in new entropy, H = SHA512(entropy || old_rng_state) is computed, and
@@ -87,7 +87,7 @@ void GetStrongRandBytes(unsigned char* buf, int num) noexcept;
  *
  * Thread-safe.
  */
-void RandAddPeriodic();
+void RandAddPeriodic() noexcept;
 
 /**
  * Gathers entropy from the low bits of the time at which events occur. Should