refactor: validate attendance in payroll

[ruchamahabal]

1. Incorrect message for completely marked attendance Ref Issue

Before:

"Attendance records not found" is a misleading message here. It actually means attendance is already marked and the list is empty.

After:

2. Employees having 0 attendance records in the month are not flagged at all

Before:

Here, all the employees have unmarked attendance but only 2 are shown (they have some records, others have 0). So they get left out in an inner join query

After:

Fetching employee attendance via left join to include employees with 0 records too. All flagged:

3. Employees having relieving date in mid-month are also flagged in spite of complete attendance

Before:

Rucha Mahabal is flagged as unmarked attendance. Relieving date (18th July). All attendance records have been marked till the 18th.

After:

Not flagged:

4. Poor view enhanced

After:

• Showing the number of unmarked days
• Pointing to the monthly attendance sheet, where users can check the exact days and then mark attendance.

Others:

• refactor: decoupled functions, better naming, remove unnecessary code
• test

[codecov-commenter]

Codecov Report

Merging #705 (a9a4ed0) into develop (f350529) will increase coverage by 0.31%.
The diff coverage is 94.11%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #705      +/-   ##
===========================================
+ Coverage    72.60%   72.92%   +0.31%     
===========================================
  Files          193      193              
  Lines         9975     9982       +7     
===========================================
+ Hits          7242     7279      +37     
+ Misses        2733     2703      -30     

Impacted Files	Coverage Δ
...rms/payroll/doctype/payroll_entry/payroll_entry.py	85.68% <93.93%> (+5.39%)	⬆️
hrms/hr/doctype/shift_type/shift_type.py	94.59% <100.00%> (+1.80%)	⬆️