fix nrows when skip_empty_area=False; increase performance for some c…

[dimastbk]

1. Fix nrows attribute of to_python when skip_empty_area is False
2. Increase performance, when nrows is small and skip_empty_area is False. Below is a benchmark for reading files from https://github.com/MarkPflug/Benchmarks/tree/main/source/Benchmarks/Data using pandas.read_excel (first - all file, second - first 10 rows).

Before:

[75.00%] ··· io.excel.ReadExcel.time_read_excel                                                                   1/10 failed
[75.00%] ··· ========== ============ ============ ============ ============ =========
             --                                      ext                             
             ---------- -------------------------------------------------------------
               engine       ods          xlsx         xlsm         xlsb        xls   
             ========== ============ ============ ============ ============ =========
              calamine   1.62±0.01s   1.47±0.01s    1.47±0s      926±5ms     956±3ms 
              default      failed      5.31±0s     5.31±0.01s   3.60±0.01s   1.31±0s 
             ========== ============ ============ ============ ============ =========
             For parameters: 'default', 'ods'
             
             
             asv: benchmark timed out (timeout 60.0s)

[100.00%] ··· io.excel.ReadExcelNRows.time_read_excel                                                    1/10 failed
[100.00%] ··· ========== ========= ============= ============= ============= ==========
              --                                      ext                              
              ---------- --------------------------------------------------------------
                engine      ods         xlsx          xlsm          xlsb        xls    
              ========== ========= ============= ============= ============= ==========
               calamine   921±8ms     761±9ms       763±8ms       221±3ms     232±10ms 
               default     failed   13.8±0.09ms   13.8±0.07ms   62.2±0.08ms   794±2ms  
              ========== ========= ============= ============= ============= ==========
              For parameters: 'default', 'ods'
              
              
              asv: benchmark timed out (timeout 60.0s)

After:

[75.00%] ··· io.excel.ReadExcel.time_read_excel                                                                                                                           1/10 failed
[75.00%] ··· ========== ============ ============ ============ ========== =========
             --                                     ext                            
             ---------- -----------------------------------------------------------
               engine       ods          xlsx         xlsm        xlsb       xls   
             ========== ============ ============ ============ ========== =========
              calamine   1.60±0.01s   1.51±0.01s   1.50±0.01s   954±20ms   930±4ms 
              default      failed     5.31±0.01s   5.35±0.01s   3.63±0s    1.32±0s 
             ========== ============ ============ ============ ========== =========
             For parameters: 'default', 'ods'
             
             
             asv: benchmark timed out (timeout 60.0s)

[100.00%] ··· io.excel.ReadExcelNRows.time_read_excel                                                                                                                      1/10 failed
[100.00%] ··· ========== ========= ============ ============ ============ =========
              --                                    ext                            
              ---------- ----------------------------------------------------------
                engine      ods        xlsx         xlsm         xlsb        xls   
              ========== ========= ============ ============ ============ =========
               calamine   795±2ms    638±1ms      639±2ms     98.4±0.3ms   109±1ms 
               default     failed   14.4±0.1ms   14.3±0.4ms   62.8±0.4ms   810±4ms 
              ========== ========= ============ ============ ============ =========
              For parameters: 'default', 'ods'
              
              
              asv: benchmark timed out (timeout 60.0s)