Reject eth_getEncryptionPublicKey for ledger hw wallets

[tmashuang]

Fixes #10111

Determine if the msgParams/address for the newRequestEncryptionPublicKey is a ledger keyring via getKeyringForAccount and return a promise rejection.

Manual testing steps:

• Connect a Ledger HW wallet
• Attempt to get an encryption key for Ledger.
• Should reject with the error message Ledger does not support eth_getEncryptionPublicKey.

[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[metamaskbot]

Builds ready [746210a]

• builds: chrome, firefox, opera
• bundle viz: background, ui, inpage, contentscript, ui-libs, bg-libs, phishing-detect
• code coverage: Report
• dep viz: background
• all artifacts

Page Load Metrics (714 ± 51 ms)

Platform	Page	Metric	Min (ms)	Max (ms)	Average (ms)	StandardDeviation (ms)	MarginOfError (ms)
Chrome	Home	firstPaint	51	94	68	9	4
		domContentLoaded	432	922	713	107	51
		load	433	923	714	107	51
		domInteractive	432	922	712	107	51

[brad-decker]

result

Tested with my Ledger, LGTM