feat: display fee settings on Send page

[theborakompanioni]

Partly addresses #518.
Display values based on fee settings in the confirmation modal of the Send page.

"Mining fee target" will be displayed either as "targeted blocks" or "sats/vByte" (randomized or exact):
e.g.

• "Next block" (tx_fees := 1)
• "In 6 blocks" (tx_fees := 6)
• "In 1,000 blocks" (tx_fees := 1000)
• "1.001 sats/vByte" (tx_fees := 1001, tx_fees_factor := 0)
• "9.1 - 10.9 sats/vByte" (tx_fees := 10000, tx_fees_factor := 0.9)

"Estimated Max. Collaborator Fee" will be displayed for collaborative transactions.
Calculation can be found here: https://github.com/joinmarket-webui/jam/blob/feat/display-fee-settings-in-send/src/hooks/Fees.ts#L69-L70 (Tests: https://github.com/joinmarket-webui/jam/blob/feat/display-fee-settings-in-send/src/hooks/Fees.test.ts#L22-L69)

📸

sats/vByte with randomization

sats/vByte exact

Targeted blocks

Collaborative transaction

[dergigi]

Code looks good to me, tACK ✅

Please have a look at the adjustments I made. Feel free to merge in case you agree with them.

[dergigi]

Screenshot for reference:

[dergigi]

Calculations were always correct for me btw. - great job on the tests 👏