Performance tuning for getProjectFiles

[takanakahiko]

Relate #610

In getProjectFiles, the process of checking for file name conflicts is very heavy.
However, this process was placed before filtering files using ignore.
That is, this process was applied to a large number of files (for example, files in node_modules), and spend long time.

Therefore, Ie speeded up by replacing the processing order.
The process of checking for file name conflicts is running before filtering words by ignore.

• npm run test succeeds.
• npm run lint succeeds.
• Appropriate changes to README are included in PR.

[grant]

Thanks @takanakahiko.

Can you test the before PR and after PR to ensure this change is an improvement?

Run time clasp push with your project. Example:

time clasp push
└─ appsscript.json
Pushed 1 file.

real	0m3.354s
user	0m1.580s
sys	0m0.263s

[takanakahiko]

@grant OK!
The results are listed below.

# Before
❯ time clasp push
└─ appsscript.json
└─ src/index.ts
└─ src/sheet.service.ts
└─ src/util.ts
Pushed 4 files.
clasp push  4.03s user 0.59s system 79% cpu 5.818 total

# After
❯ time clasp push
└─ appsscript.json
└─ src/index.ts
└─ src/sheet.service.ts
└─ src/util.ts
Pushed 4 files.
clasp push  1.96s user 0.58s system 44% cpu 5.776 total