GTiff: MultiThreadedRead(): make it take into account AdviseRead() limit to reduce the number of I/O requests

[rouault]

Fixes #9682

With those changes, the number of GET requests for #9682 use case is down to 6:

$ time GDAL_NUM_THREADS=4 CPL_DEBUG=ON python -c "from osgeo import gdal; gdal.UseExceptions(); src=gdal.Open('/vsicurl/http://localhost:8080/ortho.tiff'); src.ReadAsArray()"
HTTP: libcurl/7.68.0 GnuTLS/3.6.13 zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh/0.9.3/openssl/zlib nghttp2/1.40.0 librtmp/2.3
VSICURL: GetFileSize(http://localhost:8080/ortho.tiff)=279686928  response_code=200
VSICURL: Downloading 0-16383 (http://localhost:8080/ortho.tiff)...
VSICURL: Got response_code=206
VSICURL: Downloading 32768-49151 (http://localhost:8080/ortho.tiff)...
VSICURL: Got response_code=206
GTiff: Using up to 4 threads for compression/decompression
GDAL: GDALOpen(/vsicurl/http://localhost:8080/ortho.tiff, this=0x2ec3e50) succeeds as GTiff.
VSICURL: Downloading 16384-32767 (http://localhost:8080/ortho.tiff)...
VSICURL: Got response_code=206
GTiff: Splitting request (0,0,7255x6234) into (0,0,7255x3072) and (0,3072,7255x3162)
VSICURL: AdviseRead(): fetching 1 ranges
VSICURL: Downloading 70597872-156443454 (http://localhost:8080/ortho.tiff)...
GDAL: GDAL_CACHEMAX = 1587 MB
GTiff: Splitting request (0,3072,7255x3162) into (0,3072,7255x1536) and (0,4608,7255x1626)
VSICURL: AdviseRead(): fetching 1 ranges
VSICURL: Downloading 156443463-234346925 (http://localhost:8080/ortho.tiff)...
VSICURL: AdviseRead(): fetching 1 ranges
VSICURL: Downloading 234346934-279686923 (http://localhost:8080/ortho.tiff)...
GDAL: GDALClose(/vsicurl/http://localhost:8080/ortho.tiff, this=0x2ec3e50)

real	0m2,144s
user	0m3,233s
sys	0m3,385s

[coveralls]

coverage: 69.026% (+0.001%) from 69.025%
when pulling 5b948d1 on rouault:fix_9682
into eff42b8 on OSGeo:master.