Migrate a few flags to the new config

[kislaykishore]

Description

Migrate the following flags to the new config:

• app-name
• foreground
• rename-dir-limit
• billing-project
• limit-bytes-per-sec
• limit-ops-per-sec
• stackdriver-export-interval
• experimental-opentelemetry-collector-address
• experimental-enable-json-read
• temp-dir
• enable-nonexistent-type-cache
• file-mode
• dir-mode
• uid
• gid

Link to the issue in case of a bug fix.

NA

Testing details

1. Manual - Tested manually to see that the flags are correctly being reflected.
2. Unit tests - Existing unit-tests in legacy_param_mapper.go should already cover it.
3. Integration tests - NA

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 27.02703% with 27 lines in your changes missing coverage. Please review.

Project coverage is 72.24%. Comparing base (8637ce1) to head (e1ee4c3). Report is 1 commits behind head on master.

Files	Patch %	Lines
cmd/mount.go	0.00%	18 Missing :warning:
cmd/legacy_main.go	30.76%	9 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2089 +/- ## ========================================== - Coverage 72.25% 72.24% -0.01% ========================================== Files 101 101 Lines 10955 10956 +1 ========================================== Hits 7915 7915 - Misses 2711 2712 +1 Partials 329 329 ``` | [Flag](https://app.codecov.io/gh/GoogleCloudPlatform/gcsfuse/pull/2089/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/GoogleCloudPlatform/gcsfuse/pull/2089/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform) | `72.24% <27.02%> (-0.01%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=GoogleCloudPlatform#carryforward-flags-in-the-pull-request-comment) to find out more.

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