Support for 1.25MHz capture (#1418)

* Advanced draft decim /4 just waterfall ok

* apply some Kall's corrections + formatting

* Tidy up both decim_factors

* New refine optimizations

* Format issues

* more format issues ...mmmm

* comments update

* WIP Cleanup

* WIP

* WIP - add variant

* Use std::visit to dispatch MultiDecimator -- fluent API

* Clean up comments

* Merge next and fix compilation

* Fix odd loop in BlockDecimator

* Clean up spectrum math

* Descibe spectrum update math better, more clear math.

* Apply spectrum interval correction at 1.5M

* Increase replay buffer to handle x4 ovs

---------

Co-authored-by: Brumi-2021 <ea3hqj@gmail.com>

firmware/application/freqman_db.cpp

@@ -83,16 +83,22 @@ options_t freqman_bandwidths[4] = {
         {"100k", 100000},
         {"150k", 150000},
         {"250k", 250000},
-        {"500k", 500000}, /* Previous Limit bandwith Option with perfect micro SD write .C16 format operaton.*/
-        {"600k", 600000}, /* We doubled x2 previous REC BW limit , now extended BW from 600k to 1M with fast enough SD card in C16 or C8 format .*/
-        {"650k", 650000},
+        {"500k", 500000},
+        {"600k", 600000},
         {"750k", 750000},
-        {"1000k", 1000000}, /* New limit bandwith option for recording in C16 (in fast SD card) or in C8 */
-        {"1500k", 1500000}, /* From this BW onwards, the LCD is ok, but M4 CPU is having periodical sample rec dropps, (not real file size, accelerated replay) */
+        {"1000k", 1000000},  // Max bandwith for recording in C16 (with fast SD card).
+        {"1250k", 1250000},
+        {"1500k", 1500000},
         {"1750k", 1750000},
         {"2000k", 2000000},
-        {"2500k", 2500000},
-        {"2750k", 2750000},  // That is our max Capture option, to keep using later / 8 decimation (22Mhz sampling  ADC)
+        {"2250k", 2250000},  // Max bandwith for recording in C8 (with fast SD card).
+        {"2500k", 2500000},  // Here and up, LCD is ok, but M4 CPU drops samples.
+        {"3000k", 3000000},
+        {"3500k", 3500000},
+        {"4000k", 4000000},
+        {"4500k", 4500000},
+        {"5000k", 5500000},
+        {"5500k", 5500000},  // Max capture, needs /4 decimation, (22Mhz sampling ADC).
     },
 };