Use only filecoin mainnet by default

[cypt4]

Use only filecoin mainnet by default
Resolves brave/brave-browser#23367
Put filecoin testnet under feature flag, mainnet is by default

Submitter Checklist:

• I confirm that no security/privacy review is needed, or that I have requested one
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally: npm run test -- brave_browser_tests, npm run test -- brave_unit_tests, npm run lint, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https:/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https:/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https:/brave/brave-browser/wiki/Fingerprinting-Protections
  • https:/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https:/brave/brave-browser/wiki/Custom-Headers
  • https:/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https:/brave/brave-browser/wiki/QA-Guide
  • https:/brave/brave-browser/wiki/P3A

Test Plan:

1. Create new wallet
2. Check that there is no filecoin testnet or localhost in network list.
3. Add filecoin acc with different ways(via create, import and hardware import).
4. Check that all dialogs don't contain network chooser and will create filenet account.
5. Check that all accounts starts with 'f'.
6. Make filecoin transaction to created accounts and then back from account with mainnet filecoins.

Please note that there may be artifacts when update brave with existed filecoin accs created before this PR, but it is ok because real users don't have filecoin accs yet.

[yrliou]

As mentioned in DM, please add comment here to explain why this is fine for now.

[yrliou]

LGTM

[Douglashdaniel]

Can we update this line
https:/brave/brave-core/blob/master/components/brave_wallet_ui/components/desktop/network-filter-selector/index.tsx#L94

to something like this

{/* Disabled Filecoin Submenu until testnetworks are enabled */}
{isTestNetworksEnabled && network.coin !== BraveWallet.CoinType.FIL &&

That away it will prevent this Submenu for Filecoin until test networks are supported.

[cypt4]

Done

[Douglashdaniel]

LGTM

[srirambv]

Verification passed on

Brave	1.41.61 Chromium: 103.0.5060.42 (Official Build) nightly (64-bit)
Revision	de0d840bf9439c31bd86bf74f065c31fdf9b208d-refs/branch-heads/5060@{#667}
OS	Windows 11 Version 21H2 (Build 22000.708)

• Verified test plan from PR
• Verified only mainnet account for Filecoin is created
• Verified importing via hardware key works fine
• Verified when testnets are enabled, there is not Filecoin Testnet or Filecoin Localhost is shown in the network selector dropdown
• Encountered #23441

Create Account	Import from Ledger	Testnets
13762-Create.Account.mp4	13762-Import.from.Ledger.mp4	13762-Testnets.mp4

[srirambv]

Still need to verify the transactions on mainnet. Should be ready for uplift once its done.

Edit: Verified sending FIL coin on mainnet works fine.