update gas estimates when gas fields are changed

[josheleonard]

Description

We should refetch the gas estimates when the user changes any gas setting.

Steps to Reproduce

1. create a new EVM transaction
2. edit the gas setting for the transaction

Actual result:

the gas estimates do not immediately refresh

Expected result:

the gas estimates should refresh

Reproduces how often:

Easy

Brave version (brave://version info)

Version/Channel Information:

• Can you reproduce this issue with the current release?
• Can you reproduce this issue with the beta channel?
• Can you reproduce this issue with the nightly channel?

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields?
• Does the issue resolve itself when disabling Brave Rewards?
• Is the issue reproducible on the latest version of Chrome?

Miscellaneous Information:

[srirambv]

Verification passed on

Brave	1.64.102 Chromium: 122.0.6261.111 (Official Build) beta (64-bit)
Revision	c9343c77bd5dee3524fc45f89721ce0bf4c09b8d
OS	Windows 11 Version 23H2 (Build 22631.3155)

• Verified steps from issue description
• Verified gas estimates is updated when gas fields are changed

35518.mp4