Align audio/i2s aliases

Summary

From https://github.com/zephyrproject-rtos/zephyr/pull/114415#discussion_r3978599828:

Many audio and I2S aliases are created according to their function, rather than their purpose, while it is not relevant to it. For instance:

• samples/i2s/i2s_codec uses alias i2s-codec-tx https://github.com/zephyrproject-rtos/zephyr/blob/v4.4.2/samples/drivers/i2s/i2s_codec/src/main.c#L19
• samples/i2s/echo uses i2s-rx, i2s-tx or i2s-rxtx https://github.com/zephyrproject-rtos/zephyr/blob/v4.4.2/samples/drivers/i2s/echo/src/main.c#L16-L22
• tests/i2s/i2s_api uses i2s-node0 and i2s-node1 https://github.com/zephyrproject-rtos/zephyr/blob/v4.4.2/tests/drivers/i2s/i2s_api/src/i2s_api_test.h#L29-L34

This unravels the disparity regarding the uses of the i2s aliases and should be cleaned up. A tangible example is from the same PR mentioned above : while every nodes are declared in the common board device-tree, aliases can only provided in samples and tests overlays because of mutually exclusive name.

Describe the solution you'd like

I2S aliases should be generic, and clearly explains what it does.

From this I suggest the following patterns: i2s[0-9]-(?:rx|tx|rxtx)

Examples:

• i2s0-tx
• i2s1-rx
• i2s9-rxtx

Alternatives

No response

Additional Context

No response